analab nervous system 2nd quarter

1. Sensory input

2. Integration

3. Motor input

Function of Nervous System

Sensory input

Sensory receptors

monitor changes, called

-, occurring inside

and outside the body

Integration

Nervous system processes and interprets sensory input

and decides whether action is needed

Motor output

A response, or effect, activates muscles or glands

Central nervous system

Brain and spinal cord

Peripheral nervous system

(cranial and spinal nerves)

Sensory (afferent)

Motor (efferent)

2 kinds of PNS

Somatic, Autonomic

2 kinds of Motor Efferenr

Somatic

(voluntary)

Skeletal

muscles

Autonomic, para sympathetic and sympathetic

(involuntary)

Cardiac and

smooth muscle,

glands “we also have two type”

Structures

Activities

Nervous system

classifications are

based on:

Neuroglia

Support cells in the CNS are grouped together as -

 General functions

 Support

 Insulate

 Protect neurons

Supporting cells

Neurons

Nervous tissue is made up of two principal cell types

Supporting cells (neuroglia, glial cells,, glia)

 Resemble neurons

 Unable to conduct nerve impulses

 Never lose the ability to divid

1. Astrocytes

2. Microglia

3. Ependymal cells

4. Oligodendocytes

CNS glial cells

Astrocytes

 Abundant, star-

shaped cells, most versatile and abundant

Astrocytes

Brace and anchor

neurons to blood

capillaries

Astrocytes

Determine permeability and exchanges between blood

capillaries and neurons

Astrocytes

Protect neurons from harmful substances in blood

Astrocytes

Control the chemical environment of the brain

Microglia

Spiderlike phagocytes

Microglia

Monitor health of nearby neurons

Microglia

Dispose of debris

Microglia

Are phagocytes that defend cns cells

Ependymal cells

Line cavities of the brain and spinal cord

Ependymal cells

Cilia assist with circulation of cerebrospinal fluid

Ependymal cells

Lines CSF cavitoes

Oligodendocytes

Wrap around nerve fibers in the central nervous

system

Oligodendocytes

Produce myelin sheaths

Oligodendocytes

Have processes that forms myelin sheath around cns nerve fibers

1. Schwann cells

2. Satellite cells

PNS glial cells:

Scheann cells

Form myelin sheath around nerve fibers in the PNS

Satellite cells

Protect and cushion neuron cell bodies

Neurons

= nerve cells

Neurons

Cells specialized to transmit messages (nerve

impulses)

Cell body

Processes

Major regions of all neurons

Cell body

—nucleus and metabolic center of the cell

Processes

fibers that extend from the cell body

Cell body

is the metabolic center of the neuron

Cell body

Contains a Nucleus with large nucleolus

Nissl bodies

Rough endoplasmic reticulum

Neurofibrils

Intermediate filaments that maintain cell shape

1. Dendrites

2. Axons

3. Synapse

4. Synaptic cleft

Processes (fivers)

Dendrites

Conduct impulses toward the cell body

 Neurons may have hundreds of -

Axonss

conduct impulses away from the cell body

Axon, axon hillock

Neurons have only one - arising from the cell body at

the -

Axons, neurotransmitter

End in axon terminals, which contain vesicles with -

Axon terminals

-are separated from the next neuron by a

ga

Synaptic cleft

Gap between axon terminals and the next

neuron

Synapse

Functional junction between nerves where a

nerve impulse is transmitted

Myelin

White, fatty material

covering axons

 Protects and

insulates fibers

 Speeds nerve

impulse transmission

Schwann cells

wrap axons in a jelly roll–like

fashion (PNS) to form the myelin sheath

Neurilemma

• part of the Schwann cell

external to the myelin sheath

Nodes of ranvier

-gaps in myelin sheath

along the axon

Oligodendocytes

Produce myelin sheaths

around axons of the CNS

 Lack a neurilemm

Nuclei

—clusters of cell bodies in the CNS

Ganglion

Collections of cell bodies outside the

CNS in the PNS

Tracts

Bundles of nerve fibers in the CNS

Nerves

bundles of nerve fibers in the PNS

White matter

Collections of myelinated fibers

(tracts)

Gray matters

—mostly unmyelinated fibers and

cell bodies

1. Sensory afferent

2. Motor efferenr

3. Interneurons

Functional classifications of neurons

Sensory afferent

Carry impulses from the sensory receptors to the

CNS

Sensory afferent

Receptors include:

 Cutaneous sense organs in skin

 Proprioceptors in muscles and tendons

Motor efferenr

Carry impulses from the central nervous system

to viscera and/or muscles and glands

Interneurons

Cell bodies located in the CNS

 Connect sensory and motor neurons

Free nerve endings

(pain

and temperature receptors)

Meissner corpuscles

ouch receptor)

Lamellar corpuscles

(deep

pressure receptor)

Golgi tendon organ

(proprioceptor)

Muscle spindle

(proprioceptor)

Structural classifications of neurons

Based on number of processes extending from the cell

body

Multipola neurons

many extensions from the cell body

 All motor and interneurons are multipolar

 Most common structural typ

Bipolar neurons

one axon and one dendrite

 Located in special sense organs, such as nose and eye

 Rare in adults

Unipolar neuron

have a short single process leaving the

cell body

 Sensory neurons found in PNS ganglia

 Conduct impulses both toward and away from the cell body

Irritability

Ability to respond to a stimulus and convert it to a nerve

impulse

Conductivity

Ability to transmit the impulse to other neurons,

muscles, or glands

Polarized

 The plasma membrane at rest is inactive

K, na

Fewer positive ions are inside the neuron’s plasma membrane

than outside

-is the major positive ion inside the cell

-is the major positive ion outside the cell

Polarized os negative

As long as the inside of the membrane is more negative (fewer

positive ions) than the outside, the cell remains inactive

Stimulus

A - changes the permeability of the neuron’s

membrane to sodium ions

Sodium, na

Sodium channels now open, and - diffuses

into the neuron

 The inward rush of sodium ions changes the polarity at

that site and is called depolarization

Graded potential, stromg enough , sodium influx

 A - (localized depolarization) exists

where the inside of the membrane is more positive and

the outside is less positive

 If the stimulus is -, and -

great enough, local depolarization activates the neuron

to conduct an action potential (nerve impulse)

Sodium,, all or none, myelim sheaths

 If enough - enters the cell, the action potential

(nerve impulse) starts and is propagated over the

entire axon

 - response means the nerve impulse either

is propagated or is not

 Fibers with - conduct nerve impulses

more quickly

Repolarization

Membrane permeability changes again—becoming

impermeable to sodium ions and permeable to

potassium ions

 Potassium ions rapidly diffuse out of the neuron,

repolarizing the membrane

 Repolarization involves restoring the inside of the

membrane to a negative charge and the outer surface

to a positive charge

Action potential, axon terminal, calcium channels

Transmission of the

signal at synapses

 Step 1: When the

-

reaches the -, the

electrical charge

opens -

Calcium, axonal membrane

Step 2: -

in turn, causes

the tiny vesicles

containing the

neurotransmitter

chemical to fuse

with the -

Calcium, neurotransmitter

Step 3: The entry

of - into the

axon terminal

causes porelike

openings to form,

releasing the

-

into the synaptic

cleft

Neurotransmitter molecules

Step 4: The

-

diffuse across

the synaptic

cleft and bind to

receptors on the

membrane of

the next neuron

Neurotransmitter

Step5.

If enough

- is

released, a graded potential

will be generated

 Eventually an action

potential (nerve impulse)

will occur in the neuron

beyond the synapse

Neurotransmitter, enzymatic activity, electrochemical

The electrical changes

prompted by -

binding are brief

 The neurotransmitter is quickly

removed from the synapse

either by reuptake or by

-

 Transmission of an impulse is

-

Electrical

Transmission down neuron is

-

Chemical

Transmission to next neuron

is -

Reflexes

are rapid, predictable, and involuntary

responses to stimuli

Reflex arcs

Reflexes occur over neural pathways called -

Somatic autonomic reflexes

Two types of reflexes

Somatic reflexes

Reflexes that stimulate the skeletal muscles

 Involuntary, although skeletal muscle is normally under

voluntary control

Example: pulling your hand away from a hot object

Autonomic reflexes

Regulate the activity of smooth muscles, the heart,

and glands

 Example: regulation of smooth muscles, heart and

blood pressure, glands, digestive system

1. Sensory receptor

2. Sensry neuron

3. Integratiok center (cns)

4. Motor neuron

5. Effector

Five elemers of reflec arcs

Sensory receptor

reacts to a stimulus