What Type Of Tissue Receives Sensory Input, Integrates Data, And Conducts Impulses?

Content

Nervous System Review
Nervous tissue
Cerebrospinal Fluid (CSF)
Claret-Encephalon Bulwark
Major Areas of the Brain
---Cerebrum
---Functional Areas of The Cortex
---Motor Cortex
---Language Areas
---Basal Ganglia
---Thalamus
---Hypothalamus
---Limbic System
---Cerebellum
---Encephalon Stalk
---Pons
---Medulla Oblongata
Reticular Formation
ElectroEncephaloGram (EEG)
Memory
Basic Learning Behavior
Long-Term Potentiation
Memory Processing
Spinal String
Gray Matter
White Matter
Neural Reflexes
Reflex Arc

Nervous System

The nervous system has two major divisions:

one) Central nervous system (CNS) - consists of the brain and spinal cord. Functions to integrate and correlate sensory information; generates idea, perception, and emotions; forms and stores memory; regulates most of the trunk'south physiology and motility

2) Peripheral nervous arrangement (PNS) - consists of the spinal nerves, cranial nerves, and ganglia. Functions to bear messages to and from the spinal string and brain

Overview of nervous system

Terminology review

Nerve fiber - a general term for any neuronal process
Nerve - a bundle of many nerve fibers along the aforementioned path in the PNS surrounded past a connective tissue layer.
Ganglia - a cluster of nerve cell bodies in the PNS
Nucleus - a mass of cell bodies and dendrites in the CNS
Tract - a packet of nerve fibers along the same path in the CNS without a connective tissue layer.
White thing - aggregations of myelinated processes from many neurons
Gray matter - contains either neurons cell bodies, dendrites, and axon terminals, or unmyelinated axons and neuroglia

There are iii classes of neurons

1. Afferent – transmit sensory impulses from PNS to the CNS.
- Sensory afferent fibers – acquit impulses from skin, skeletal muscles, and joints
- Visceral afferent fibers – transmit impulses from visceral organs

2. Efferent - transmit motor impulses from CNS to PNS
- Somatic nervous system – provides witting command of skeletal muscles
- Autonomic nervous system – regulates smooth muscle, cardiac muscle, and glands

3. Clan neurons or interneurons All other neurons are termed as association neurons or interneurons responsible for integrating afferent data and formulating an efferent response to include college cognitive functions

Nervous tissue

Nervous tissue is fabricated upward of:

Neuroglia are specialized nervous tissue cells that are smaller and more than numerous than neurons. They serve to carry out support functions such every bit vascularization, phagocytosis and myelinization.

There are four types of neuroglia constitute in the CNS:

1. Astrocytes - star shaped with many processes, participate in the metabolism of neurotransmitters, maintain proper Grand+ residual, aid form blood brain bulwark, and provide a link between neurons and blood vessels.

ii. Oligodendrocytes - fewer processes and are smaller that astrocytes, most common type in the CNS, they are involved in myelinization.

3. Microglia - small cells derived from monocytes that part equally macrophages and carry out phagocytosis.

4. Ependymal - columnar to squamous epithelial cells ofttimes ciliated that form a lining in the ventricles (fluid filled cavities in the brain).

CNS Protection

Cranial bones
Vertebral column
Meninges (dura mater, arachnoid, pia mater)
Cerebrospinal fluid (CSF)

Cerebrospinal Fluid (CSF)

CSF is a clear, colorless liquid that nourishes and protects the CNS from chemic and physical injury
It circulates through the subarachnoid space effectually the encephalon and spinal string and through the four ventricles (cavities) inside the encephalon
It contains glucose, proteins, lactic acid urea, ions, some lymphocytes.
- Formed past selective send across ependymal cells
- Volume 125-150 ml and is replaced > 3 times/solar day, flow maintained past 10 mmHg pressure gradient
- Path: ventricles ® subarachnoid space, reabsorbed into blood in dural sinuses through arachnoid villi

Functions of CSF:
- Shock-absorbing medium
- Provides a optimum and stable environment for generating nerve impulses
- Provides a medium for the exchange of nutrients and wastes betwixt claret and nervous tissue.

Production of CSF

The choroid plexus is a network of blood capillaries in the walls of the ventricles

The capillaries are covered by ependymal cells that produces the CSF.

The ependymal cells provide a fluid tight barrier effectually the capillaries called the blood-encephalon barrie

Click hither for an animation that describes the production and menstruation of cerebrospinal fluid.

Blood-Brain Barrier

Formed by capillary endothelial cells formed with tight junctions
The tight junctions restrict transport between cells
Astrocytes induce formation of tight junctions and help control transcellular send such as K+
Some materials pass the blood-brain barrier
- - Materials that diffuse through the lipid bilayer cannot be restricted –O2, CO2, alcohol, steroids, H2O
  - Materials that require carrier send are restricted – glucose, amino acids, and ions
  - Some materials cannot pass the barrier – potentially harmful substances, some hormones/drugs
Functions of the claret-brain barrier:
- - Protects CNS from chemical fluctuations
  - Prevents entry of harmful substances
  - Prevents entry of molecules that could human activity as neurotransmitters
There are just iii places in the brain that do not have a blood brain bulwark:
1. Choroid plexuses (because they make CSF)
two. Hypothalamus (needs to let hormones into bloodstream)
3. Pineal gland (also needs to let hormones into the bloodstream)

Major Areas of the Brain

About one trillion interneurons fill the brain
Each interneuron has upwardly to 200,000 synapses each
There are several major areas of the brain:

Cerebrum (including the cerebral cortex and basal nuclei)
Thalamus
Hypothalamus
Cerebellum
Brain Stalk

Click here for an animation that summarizes the major areas of the brain and the role of each area.

Cerebrum

Includes cognitive cortex, tracts, and basal nuclei
Is highly developed
Makes up about 80% of total brain weight (largest portion of encephalon)
The inner cadre houses basal nuclei
The o uter surface is made up of the highly convoluted cerebral cortex:

Highest, virtually complex integrating surface area of the brain
Plays primal office in most sophisticated neural functions

Cerebral Cortex - (grey matter "figurer")

Each half of the cognitive cortex is divided into four major pairs of lobes

Occipital Lobes - carries out initial processing of visual input

Temporal Lobes - initial reception of sound sensation

Parietal Lobes - somatosensory processing

Frontal Lobes responsible for
- Voluntary motor activity
- Speaking ability
- Elaboration of thought

The outer layer of cerebrum hold the soma or prison cell bodies of the neurons.

Surface features of the cerebral cortex include gyri (ridges), sulci (grooves), and fissures (deep grooves)

The fissures increase the surface surface area and split up the brain into the four major pairs of lobes

Functional Areas of The Cortex

Master Somatosensory Cortex

Located in the post primal gyrus (direct posterior to central sulcus) of each parietal lobe

Receives input from somatic sensory receptors for proprioception, touch on, pain, temperature.

Primary function is to localize exact sites where sensations originate

Sensory homunculus – shows proportional distribution of sensory input to the somatosensory cortex from different parts of the trunk based on degree of sensory perception

Primary Motor Cortex

Located in the precentral gyrus of the frontal lobe

Controls voluntary contractions of specific muscles or groups of muscles.

Size of expanse and number of neurons representing each function of the body is proportional to precision and complication of movement of that function

Linguistic communication Areas

Comprehension and translating thought into voice communication involves both sensory, association, and motor speech areas located in the frontal lobe.

Broca's area – voice communication germination, speaking ability

Wernicke's expanse – linguistic communication comprehension

Primary Visual Cortex

Medial surface of occipital lobe

Receives input from the thalamus (lateral geniculate nuclei) concerning shape, colour, and motility

Main Auditory Cortex

Is located in superior part of the temporal lobe

Interprets characteristics of sound, hearing

Primary Gustatory Area

Is located at the base of post central gyrus in the parietal lobe

Receives impulses for taste

Main Olfactory Area

Located in the medial aspect of temporal lobe

Receives impulses for smell

Supplemental Motor Expanse

Plays preparatory role in programming circuitous sequences of movement

Premotor Cortex

Orients the torso and arms toward a specific target

Deals with learned motor activities of a circuitous and sequential nature.

Association Areas

Are tracts that connect motor and sensory areas and big parts of the cortex

Prefrontal Clan Cortex

Involved in planning voluntary activity, determination making, inventiveness, personality traits

Parietal-Temporal-Occipital Clan Cortex

Pools and integrates somatic, auditory, visual sensations for complex perceptual processing

Also involved with linguistic communication

Limbic Association Cortex

Involved in motivation and emotion involved with memory

Integration of Cortical Regions

Sensory input >> somatosensory cortex >> higher sensory areas >> association areas >> higher motor area >> main motor cortex >> motor output

Basal Ganglia

Is a group of nuclei (clusters of cell bodies) in each cerebral hemisphere
Regulates (inhibits) muscle tone required for polish body movements
Selects and maintains purposeful motor activity
Monitors and coordinates slow sustained contractions – posture/support

Thalamus

Is an oval structure consisting of gray matter organized into nuclei
Is the principle relay station for all sensory input to the cerebral cortex from spinal cord, encephalon stem, cerebellum and other parts of the cerebrum.
Routes important sensory impulses to appropriate areas of the somatosensory cortex.
It directs attention to stimulus of interest:

medial geniculate nuclei - hearing
lateral geniculate nuclei - vision
ventral posterior nuclei - sense of taste and somatic sensations (pain, pressure)
anterior nucleus - emotions and memory

Hypothalamus

Is located below thalamus
Is a major regulator of homeostasis
Controls and integrates activities of the autonomic nervous system (ANS)-regulates the contraction of smooth muscle, cardiac musculus and secretions of many glands.
The main regulator of visceral activities such as middle rate, GI tract movement, and bladder contraction
Associated with feelings of rage and assailment
Regulates torso temperature, food intake, and thirst
Maintains waking state and sleep patterns
Controls anterior pituitary hormone secretion
Produces and transports hormones (antidiuretic hormone-ADH) to the posterior pituitary gland.

Limbic System

Is a ring of structures encircling the encephalon stem
It includes portions of the cortical lobes, amygdala, basal nuclei, nuclei of the hypothalamus and of the thalamus, and olfactory bulbs.
Functions in the emotional attribute of behavior and in memory in conjunction with the hippocampus and cerebrum

Cerebellum

Is located posterior to medulla and pons
Is concerned with subconscious movements of skeletal muscle and equilibrium
Controls skeletal muscle contractions for skilled movements, coordination
Vestibulocerebellum – residue and command of eyemovement
Spinocerebellum – enhances musculus tone and coordinates skilled voluntary movement – important in synchronization and timing
- receives input concerning desired action from motor cortex
- receives feedback concerning actual activeness from proprioceptors, vestibular apparatus, eyes
- compares inputs and sends adjustments or corrective signals to motor tracts
Cerebrocerebellum – planning and initiation of voluntary activeness past providing input to the cortical motor areas too involved in procedural memories
Role of spinocerebellum in hidden command of voluntary motility:
Motor cortex >> command to muscles and informs spinocerebellum >> motility >> activates muscle/joint receptors >> relays bodily functioning to spinocerebellum >> comparing and adjustments fabricated every bit necessary

Brain Stem

Consists of medulla, pons, midbrain
Is an important link between spinal cord and college brain levels relays motor and sensory impulses between other "higher" parts of the encephalon and spinal cord
-Midbrain – centre movement control
Pons/Medulla
- Bespeak relay
- Involuntary functions
Many cranial nerves enter
Pyramids – nerve tracts crossover

Pons

Sensory and motor nuclei for four cranial nerves
Nuclei that help control respiration
Nuclei and tracts linking the cerebellum with the brain stem, cerebrum and spinal cord
Ascending, descending and transverse tracts

Medulla Oblongata

Contains relay stations and reflex centers:
- -Olivary nuclei
- - Cardiovascular and respiratory rhythmicity centers
- - Cardiovascular middle - regulates charge per unit and force of heartbeat and vasoconstriction/dilation
- - Respiratory center - regulates basic breathing rhythm
Reticular formation begins in the medulla oblongata and extends into more superior portions of the brainstem

Reticular Germination

Network of interconnected neurons runs throughout brain stem and into thalamus
Functions in consciousness and arousal
Receives and integrates all incoming sensory synaptic input
Reticular activating organisation (RAS) - ascending fiber sends signals upwardly to agitate and activate the cerebral cortex, controls overall caste of cortical alertness or level of consciousness - maximum alertness >> wakefulness>> sleep >> coma
Level of consciousness depends on the cyclical coaction between the RAS, a slow wave sleep center and a paradoxical sleep center both in the hypothalamus

ElectroEncephaloGram (EEG)

Records electrical activeness within cerebral cortex from EPSPs and IPSPs.
Used to diagnose:
- Cerebral dysfunction
- Encephalon death
- Sleep patterns

Function of Sleep

Is a time to restore biochemical and physiological processes degraded during slumber
Part of adenosine on sleep:
- Adenosine backbone of ATP, body's energy molecule
- Increased levels generated during wakefulness
- Adenosine as a neuromodulator has been shown to inactivate arousal center
- Caffeine blocks adenosine receptors in the brain – prevention inhibitory action on the arousal center
Sleep necessary to achieve long term structural and chemical adjustments required for learning and retentivity, specially consolidation of procedural memories

Retentiveness

Is "storage of acquired knowledge for later think"
Neural modify responsible for retention and storage of knowledge is known as the retentivity trace
Consolidation - Procedure of transferring and fixing short-term retentivity traces into long-term memory stores
Working memory - Temporarily holds and interrelates various pieces of data relevant to a electric current mental chore
Brusk term retentivity

Characteristics:
- Seconds to hours
- Express chapters
- Rapid retrieval
Mechanisms:
- Temporary modifications of synaptic part
- Changes in ion channels in the axon terminals
- Presynaptic facilitation (military camp)

Basic Learning Behavior

Habituation – decreased responsiveness to stimulus, closure of Ca channels leads to reduced neurotransmitter release
Sensitization – increase responsiveness, release of serotonin from interneuron> increment military camp in presynaptic neuron which blocks K channels > prolongs AP so Ca channels are open longer, increasing neurotransmitter output

Long-Term Potentiation (LTP)

Starts with release of glutamate from activated presynaptic neuron

> AMPA receptors > EPSPs
> NMDA receptors > open Ca channels > 2nd messenger formation > increases # of AMPA receptors
or release of nitric oxide (NO) > acts on presynaptic neuron to increment neurotransmitter release

Long Term Memory

Last days to years
Unlimited capacity
Mechanisms - permanent structural changes in the brain
- Formation of new synapses betwixt existing neurons
- Increased dendritic surface surface area
- Increase in neurotransmitter receptors
- Changes in neurotransmitter synthesis
Consolidation is afflicted past:
- Amount of rehearsal
- Association of new & old data
- Level of excitement/importance of data
- CREB – regulatory proteins that activate genes important in long term retention storage

Retentivity Processing

Hippocampus and medial temporal lobe - short term retention and consolidation declarative retentiveness (facts), specific objects, requires conscious recall

Cerebellum – "how to" memories, motor skills(procedural), subconscious recall

Prefrontal cortex - working memory, processes new and retrieved information, temporary storage, problem solving, planning, organizing

Spinal Cord

The spinal cord is a continuation of the encephalon (medulla).
Is a long cylindrical cable of nervous tissue,
Is 1-2 centimeters in diameter and extends from the foramen magnum of the skull to L1 vertebrae.
It is about 18" (42-45 cm) long
Is located in the vertebral culvert and protected by the vertebrae
Is surrounded by three protective connective tissue coverings - spinal meninges
The spinal cord, similar the brain is made upward of gray matter and white matter (the gray matter is centrally located in a butterfly shape)
31 pairs of spinal fretfulness originate from the spinal cord (spinal fretfulness are part of the PNS)
The spinal cord serves as the major pathway for impulses to and from the encephalon-
- it conveys sensory impulses from the body (from sensory receptors) to the brain
- information technology conveys motor impulses to the trunk (to muscles and glands).
The spinal cord also integrates information on its own, controlling spinal reflexes that occur without any encephalon interest (ex: withdrawal from pain)

Gray Thing

Mostly prison cell bodies

Dendrites & terminals
Spinal reflex integrating centre

White Matter

Bundles of myelinated axons
- Ascending tracts – sensory
- Descending tracts – motor
Dorsal roots
Ventral roots

Extending from the spinal string are dorsal and ventral roots which converge to grade 31 pairs of spinal nerves.
Spinal nerves provide the pathway betwixt the spinal string and most of the body.

The core - gray matter - primarily consists of cell bodies of motor neurons and nuclei (clusters of nerve cell bodies in CNS) neuroglia, unmyelinated axons and dendrites of association and motor neurons
The gray matter is shaped like an H or butterfly formed by correct and left ventral (anterior), lateral and dorsal (posterior) horns connected past the grayness commissure.

The outer portion - white matter - contains myelinated motor and sensory nervus fibers to and from the brain and other levels of the spinal cord. The white affair is made upwards of 3 wide columns ( funiculi); the anterior, lateral and posterior white columns. Each column is made up of ascending (sensory) and descending (motor) tracts.

Sensory and motor tracts of the white matter

Spinal nerves are the paths of communication between the spinal cord and about of the body. Each spinal nerve attaches to a segment of the spinal cord to grade roots.

Dorsal root - contains sensory nerve fibers and conducts nerve impulses from the periphery into the spinal cord.
Each posterior root has a swelling called the dorsal root ganglion, which contains the prison cell bodies of the sensory neurons.
Ventral root - contains motor neuron axons and conducts impulses from the spinal cord to the periphery.

Neural Reflexes

Stimulus
Sensory receptor
Sensory (afferent) neuron
CNS integration
Efferent (motor) neuron
Effector (target tissue)
Response (movement)
Feedback to CNS

Reflexes

Are fast anticipated, automated responses to changes in the surround that aid maintain homeostasis,
Reflexes are of iii types: cranial reflexes, somatic reflexes and visceral (autonomic) reflexes.

Reflex Arc -

Is the simplest pathway, involving five components
1. Receptor - distal end of a sensory neuron (dendrite) that responds to a stimulus
2. Sensory neuron/afferent pathway - conducts impulse from receptor to axon concluding located in the gray matter.
3. Integrating center in CNS - may exist monosynaptic or polysynaptic involving other association neurons
4. Motor neuron/efferent - relays impulse from integrating middle to part of the body that will respond.
5. Effector - gland or muscle that responds to motor neuron impulse.

Click hither for an animation that describes reflex arcs.

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