Nervous Tissue (chapter 12)

overall role of nervous system and describe structure of a nerve, neurons, neuroglian cells, CNS, PNS, function and synapses of potential neurotransmitters.

What does the nervous system do with other parts of the body?

Pathway of communication

Which other system do the nervous system work with ?

Endocrine system

What is homeostasis?

active maintenance of the internal conditions, even if fluctuation of external + internal environment

What does the nervous system use to respond to internal and external changes in cells enviroment?

Specialized cells, electrical, and chemical means

What does integration mean?

Detection + response = integration

It can see then integrate info and respond

What does the special cells have to be to generate nerve impulses

“exited” responding to electrical changes of ions

What does the nervous system determine for the human body?

perception, memory, behavior and movement

what are the 3 main functions of the nervous system

1. sensory function

2. integrative function

3. motor function

Sensory function

sensory neurons (receptors) detect changes in the internal and external environment TOWARD the brain and spinal cord

Integrative function

Interneurons analyze INCOMING sensory info to store some info, make decisions regarding appropriate behaviors or where they should go

Motor neurons

Motor neurons INITIATE appropriate responses to stimuli by activating effectors such as muscles and glands. info out (brain and spinal cord) and away

what are the key 2 parts of the nervous system

Central Nervous system (CNS)- brain, spinal cord

peripheral nervous system (PNS)- all other nervous tissue outside the CNS

What components are in the PNS

Nerves -that include 12 paired cranial nerves, 31 paired spinal nerves.

Sensory receptors- specialized structure in the nervous system that monitors changes in external and internal environment

The PNS are divided into which 2 divisions?

Sensory (afferent) division, Motor (efferent) division

Sensory (afferent) division (PNS)

Provides the PNS with sensory info about SOMATIC senses, and SPECIAL senses TO the

What are Somatic senses

tactile, thermal, pain, proprioceptive (movement) (body senses that anything else but your head.)

What are special senses

smell, taste, vision, hearing, equilibrium. Senses in your head

Motor (effective) division

convey output from CNS to effectors (muscles and glands)

Whats an effector

things that do stuff

What are the 2 more subdivided systems are for motor division.

Somatic nervous system, Autonomic nervous system

Somatic nervous system (motor division)

Relays outputs from CNS ONLY to skeletal muscles

voluntary= not automatic

Automatic nervous system (motor division)

Relays output to smooth muscle, cardiac muscle, and glands

involuntary= automatic

what are the 3 branches of the autonomic nervous system of Motor division

1. sympathetic

2. parasympathetic

   typically innervate the same effectors but have OPPOSING actions

3. Enteric plexuses- regulate smooth muscle and gland in digestive canal

What is the function of a neurons

electrically excitable cellular structures that generate nerve impulses (action potential)

What do Neurons DO NOT undergo?

mitotic division- neuron dies, cannot do cell divison

What do Neuroglia do?

support, protect, nourish neurons and maintain interstitial fluid. (fluid around cells to make sure ion concentration is at the best environment)

What CAN Neuroglia undergo?

mitotic cell division- if dead can undergo cell division

What is a nerve/what is it made up of?

a bundle of 100-1000s of AXONS (plus connective tissue and blood vessels) outside of brain and spinal cord.

Are nerves part of the CNS or PNS

ONLY CNS, PNS has a different name for nerves

internal structure of nerves are?

neuron axons grouped within connective tissue sheaths

what is the name of the tissue sheath of a single axon (Fiber)

Endoneurium

What is the name of the tissue sheath of a bundle of fibers (fascicle)

Perineurium

What is the name of the tissue sheath of a bundle of fascicles (nerve)

epineurium

What is the function/(s) of a Neuron

functional unit of the nervous system by connection all regions of the body to the brain and spinal cord

electrically excitable= movement of charges (ions) between the membrane length of the cell (AP)

transmit Signals from one cell to another through APs

what is the cell body called in a neuron

(soma)

Whats in a Cell body of a neuron. (6)

Nucleus, Nissl bodies (Rough ER), ribosomes, Neurofibrils (structure), Microtubules (highway/transport from vesicles from one side of the end to the other), mitochondria/mitochondrion

what are the Cell processes of the nerve fibers (2)

dendrites, axons

Dendrites (have and look like)

short, branched and unmyelinated

neurofibrils, nissl bodies

Dendrites function (3)

receiving part of the neuron (into)

conduct nerve impulses TOWARD the cell body, to makes contact with other cells

contain numerous receptor sites for binding chemical messenger from other cells (signal to start)

Axon (have and look like)

single long process

Axoplasm (cytoplasm), is surrounded by the Axolemma (plasma membrane)

Axon function

acts as a trigger zone, conduct nerve impulses away from the cell body to other neurons, muscles, or gland cells

What is the end in fine process called for Axons?

Axon terminals

what is a the end of an Axon terminal and what does it do?

Synaptic end bulbs contain synaptic vesicles that store neurotransmitters

What are the two terminology for cluster of cell bodies

Nucleus= neuronal cell bodies in CNS

Ganglian= neuronal cell bodies in PNS

What are the two terminology for bundles of axons

tracts = CNS

nerves= PNS

How can we classify Neurons?

diverse in shape and size, structural classification is based on the number of processes extending from the cell body

What are the 3 types of neurons based on structure?

1. Multipolar neuron

2. Bipolar neuron

3. pseudounipolar/unipolar neuron

Multipolar Neuron

Structure: several dendrites, but only ONE axon

ALL motor neurons and “most” CNS neurons (interneurons and multipolar)

Bipolar Neuron

Structure: one dendrite and one axon

found in retina, inner ear, olfactory area of the brain, (balance, sight)

Psudounipolar/unipolar neuron

Structure: one fused dendrite and axon

Dendrites act as sensory receptors for stimulus (touch, pain, pressure, thermal, Somatic senses)

What is functional classification of neurons based on?

direction of nerve impulse propagation

What are the 3 function classification based on direction?

1. Sensory (afferent- towards CNS neurons)

2. Motor (efferent- away from the neurons from the CNS) neurons

3. interneurons (association within CNS)

Sensory (afferent- towards CNS neurons)

(describe pathway)

forms nerve impulses in response to stimuli , then sends impulse to the CNS through cranial and spinal nerves

Motor (efferent- away from the neurons from the CNS) neurons

(describe pathway)

Sends commands from CNS to muscles and glands (effectors) through cranial and spinal nerves

interneurons (association within CNS)

(describe pathway)

process incoming sensory information and initiates motor response

Connects sensory to motor neurons in the CNS

What are the 6 types of Neuroglia

Neuroglia of the CNS (4)

-Astrocytes, oligodendrocytes, microglial cells, and ependymal cells

Neuroglia of the PNS (2)

-Shwann cells, satellite cells

CNS neuroglial cells: Astrocytes

Structure, types (2)

largest, most numerous neuroglia cells, STAR SHAPED, processes contact other cells

1. protoplasmic astrocytes-short branching processes

2. fibrous astrocytes- long unbranched processes

CNS neuroglial cells: Astrocytes function (5)

1. provide structural support (hold in place for neurons)

2. help form blood brain barrier

3. regulate ion and neurotransmitter concentrations in interstitial fluid

4. help in information of neural synapse (site of nerve impulse transmission),

5. regulate chemicals needed for neuron development in embryos

CNS neuroglial cells: Oligodendrocytes

Structure, function

smaller than astrocytes, fewer processes than astrocytes

Function: form a

Myelin stealth is?

Multilayered lipid and protein covering

CNS Neuroglial cells: microglial cells

Structure, function

small cells, slender processes

Function: Phagocytic cells (eat stuff/debris/microbes/damaged tissue), refine synapses during development using phagocytosis, immune cell of the CNS