NervousTissue.ppt

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Nervous Tissue

Pages 236-252

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I. Functions

A.

Sensory input – senses stimuli occurring

inside and outside of the body

A.

Integration – analyzes sensory information in

order to make a decision

A.

Motor output – response to stimuli by

activating muscles, glands, or other parts of

(3)

II. Structural Organization

A.

A. Central Nervous Central Nervous

System (CNS) is System (CNS) is composed of

composed of 1. Brain

1. Brain

2. Spinal Cord 2. Spinal Cord

B. Peripheral Nervous B. Peripheral Nervous

System (PNS) is System (PNS) is composed of

composed of

(4)

III. Histology

A.

Neurons – conduct nervous impulses from one

part of the body to another; basic information

processing unit

1.

Structure

a. Dendrites – initially receive

impulses

and carry them to the cell

body

b. Cell body – contains the nucleus

and

(5)

i.

i. Axon terminalAxon terminal – end of axon – end of axon ii.

ii. Synaptic end bulbsSynaptic end bulbs – ends of axon terminals; – ends of axon terminals; form junctions with muscle, nervous, or glandular form junctions with muscle, nervous, or glandular

tissue tissue

iii.

iii. MyelinMyelin – lipid-protein covering that – lipid-protein covering that protects, protects, insulates, and speeds transmission

insulates, and speeds transmission iv.

iv. Schwann cellsSchwann cells – (neurolemmacytes – not – (neurolemmacytes – not part part of the CNS), produce myelin

of the CNS), produce myelin v.

v. Nodes of RanvierNodes of Ranvier – spaces on the axon – spaces on the axon between Schwann cells

between Schwann cells vi.

vi. NeurolemmaNeurolemma – sheath covering Schwann – sheath covering Schwann cellscells C. Axons – extension that sends impulse to another C. Axons – extension that sends impulse to another

(6)

(7)

2. Types of Neurons

a.

a. SensorySensory (afferent) – (afferent) –

conduct impulses to the conduct impulses to the brain and spinal cord

brain and spinal cord

b.

b. MotorMotor (efferent) – (efferent) –

conduct impulses away conduct impulses away from the brain and

from the brain and

spinal cord to muscles spinal cord to muscles and glands

and glands

c.

c. InterneuronsInterneurons – conduct – conduct

impulses from sensory impulses from sensory neurons to motor

neurons to motor neurons

(8)

B. Neuroglia – function in support,

insulation, and protection

1.

Type in the CNS

a.

Astrocyte

– star shaped cells that hold

bloood vessel to neurons

b.

Microglia

– phagocytic cells that

monitor the CNS

c.

Oligodendrocyte

– form myelin sheaths

in CNS

d.

(9)

2. Types in the PNS

a.

Schwann cells – produces myelin

sheaths for PNS

b.

Satellite cells – support neurons in

(10)

C. Axon bundles

1.

In the PNS the bundles form WHITE

MATTER, they are white because of

the myelin, the white matter

propagates nerve signals.

2.

In the CNS the cell bodies and

unmyelinated axons are called

GRAY MATTER. This tissue

(11)

IV. Nerve Impulses – tiny electric currents that

travel along the surface of a neuron

membrane

A.

Na-K pump

– ion gated; functions in

transmitting the impulses

1. This process propagates the nerve

signal down the axon.

2. The charges on the Na and the K

changes the charge on each side of the

(12)

(13)

B. Functions

1.

Excitability – the ability to respond

to a stimulus and convert it into a

nerve impulse (electrochemical)

a. Threshold stimulus – any

stimulus that is strong enough to

initiate a nerve impulse

b. All or none response – once the

threshold is reached, the impulse is

conducted down the entire axon at

(14)

c. Stimulus changes the permeability

to the neuron membrane allowing

Na+ to enter the cell (

depolarization

)

d. Electrical condition of the resting

stage (

polarized

) is restored by the

diffusion of K+ out of the cell, this is

called

(15)

(16)

2. Conductivity – the ability to

transmit the impulse to the other

neurons, muscles, or glands

a.

Neurotransmitters are released from

the axon terminal of a presynaptic

neuron into the synaptic cleft

b.

Neurotransmitter binds to a specific

molecule in the membrane of a

postsynaptic neuron. This stimulates

the impulse conduction by the

(17)

Spinal Cord and Brain

I.

I. Meninges are Meninges are

connective tissues that connective tissues that cover the organs of the cover the organs of the CNS

CNS

a. Dura Mater (

a. Dura Mater (tough tough

mother)

mother) – outermost – outermost

layer; provides protection layer; provides protection for the organ

for the organ b.

b. Arachnoid mater – Arachnoid mater –

middle layer; resembles middle layer; resembles a spider web

a spider web c.

c. Pia Mater – inner layer; Pia Mater – inner layer;

adheres to the surface of adheres to the surface of the organ

(18)

II. Spinal Cord

A.

A. Location – extends Location – extends

from magnum foreman from magnum foreman of the occipital bone to of the occipital bone to the second lumbar

the second lumbar vertebrae.

vertebrae.

B.

B. Cauda equina Cauda equina (horse’s (horse’s

tail) – nerves arising tail) – nerves arising from the spinal cord. from the spinal cord.

C.

C. H-shaped interior H-shaped interior

portion is gray matter. portion is gray matter.

D.

D. Outer portion is called Outer portion is called

white matter; tracts white matter; tracts called

called

(19)

E. Functions

A.

Primary reflex center

1. Reflex arcs – conduction of nerve

impulses results in a reflex.

2. Somatic arcs control skeletal muscle

3. Autonomic arcs control smooth and

cardiac muscle and glands

B. Sensory impulses ascend through tracts

(20)

III. Brain is composed of about 100

billion neurons and weighs about 3

lbs.

A.

A. CerebrumCerebrum

1.

1. Largest part of brainLargest part of brain 2.

2. Ridges are called gyrus made by Ridges are called gyrus made by the folds

the folds 3.

3. Spaces between the gyrus are Spaces between the gyrus are called sulci

called sulci 4.

4. Deepest sulci are fissuresDeepest sulci are fissures a.

a. Longitudinal fissure Longitudinal fissure divides divides the cerebrum into the left and the cerebrum into the left and right hemispheres joined

right hemispheres joined together by the

together by the corpus corpus collosum

collosum and allows the right and allows the right and left to communicate

(21)

b.

Central Fissure

(fissure of

Rolando)

separates frontal and

parietal lobes

c.

Lateral fissure

separates frontal

(22)

5. Lobes are identified by the bones

that cover them

a.

a. FrontalFrontal

i. Motor skills (located in i. Motor skills (located in precentral gyrus)

precentral gyrus)

ii. Broca’s area – generally ii. Broca’s area – generally on the left side, controls on the left side, controls motor speech

motor speech

iii. Intelligence and iii. Intelligence and abstract reasoning abstract reasoning

b. Parietal b. Parietal

i. Somatic sensory area i. Somatic sensory area ii. Reading

(23)

c. Temporal

i. Auditory

ii. Language/speech comprehension

d. Occipital

i. Visual

6.

Cerebral cortex

– the thin layer of

gray matter (non-myelinated) on the

(24)

7. Interior of the brain

is composed of white

matter (myelinated)

a. Within the white

matter there are

paired masses of

gray matter called

basal nuclei

that

control skeletal

muscle movements.

(25)

8. Diencephalon –

interbrain; lies on top of

the brain stem and is

enclosed by the cerebral

hemispheres

a. Thalamus – dumbbell

shaped mass of gray

matter in each cerebral

hemisphere

i. relays sensory

impulses to cerebral

cortex sensory areas

ii. Produces emotions of

pleasantness and

unpleasantness with

(26)

b. Hypothalamus – consists mainly

of the posterior pituitary gland,

pituitary stalk, and gray matter

i.

i. Major center for Major center for

controlling the ANS controlling the ANS (controls internal (controls internal organs)

organs)

ii.

ii. Controls hormone Controls hormone

secretions by anterior secretions by anterior and posterior pituitary and posterior pituitary gland

gland

iii.

iii. Contains center for Contains center for

controlling normal body controlling normal body temp, feeling of pain, temp, feeling of pain, rage, aggression,

rage, aggression, pleasure, appetite, pleasure, appetite, thirst, and sleep thirst, and sleep patterns

(27)

c. Pituitary gland –

master gland in

body

d. Pineal gland –

melatonin secretion

controls the body’s

(28)

IV. Cerebellum

a.

a. Second largest part of Second largest part of

brain brain

b.

b. Composed of an outer Composed of an outer

layer of gray matter and layer of gray matter and an inner layer of white an inner layer of white matter

matter

c.

c. Lies behind the medulla Lies behind the medulla

and pons and under the and pons and under the occipital lobe

occipital lobe

d.

d. Functions include muscle Functions include muscle

coordination, equilibrium, coordination, equilibrium, memory, and regulation of memory, and regulation of balance and posture

(29)

V. Brain Stem

A.

Medulla Oblongata

1. Located in the inferior and

posterior portion of the cranial

cavity; just superior to the foramen

mangnum

2. Contains all sensory (ascending)

tracts and motor (descending) tracts

that run between the brain and

spinal cord

(30)

3. The white and gray matter are closely 3. The white and gray matter are closely

intertwined intertwined

4. The

4. The pyramidspyramids – 2 triangular structures that – 2 triangular structures that make up the medulla; contain the motor tract make up the medulla; contain the motor tract

(31)

5. The pyramid on the right side

controls the left side of the body and

visa versa

6. Controls vital center functions

(32)

II. Pons

1.

Located superior

to the medulla

2.

Gray and white

matter

arrangement

similar to that of

medulla

3.

Some of the

cranial nerves

(33)

III. Midbrain

1.

Extends from lower

portion of pons to

the diencephelon

2.

Connect cerebral

cortex with the

pons and the spinal

cord

3.

Some of the cranial

nerves originate

(34)

IV. Throughout the brain stem, the

midbrain, and the diencephalon is

the

reticular formation



The reticular

formation is a

netlike group of

neurons. It

receives and

integrates input

from the cerebral

cortex, cerebellum,

and spinal cord

(35)

V. Cerebrospinal Fluid

1.

Fills spaces in the

brain called

ventricles.

2.

2 Functions:

Protection &

circulation

3.

Formed by the

choroid

plexuses

(36)

PNS

I.

Cranial Nerves

A. 12 pair that attach to the

undersurface of brain

B. Connect brain with the neck and

structures in the throat and

(37)

(38)

C. Nerves

1.

Olfactory (1) {sensory} – sense of smell

2.

Optic (2) {sensory} – vision

3.

Oculomotor (3) {motor} – eyeball &

eyelid movements and pupil constriction

4.

Trochlear (4) {motor} – eye movements

(superior oblique)

5.

Trigeminal (5) {both} – sensation of the

face, oral cavity, and chewing

6.

Abducens (6) {motor} – turning eyes out

(lateral rectus)

(39)

Cranial Nerves, Cont.

7. Facial (7) {both} – sense of taste,

contraction of the facial, throat, and ear

muscles

8. Vestibulocochlear (8) {sensory} – hearing

and balance

9. Glassopharyngeal (9) {both} – sensation

of throat and taste; swallowing

10. Vagus (10) {both} – extends to

abdomen; sensation of throat, larynx, and

thoracic and abdominal organs (and

regulation), moves tongue, voice production

(40)

Cranial Nerves, Cont.

11. Accessory (11) {motor} –

shoulder movements, turning head

12. Hypoglossal (12) {motor} –

tongue movements

O

h

O

nce

O

ne

T

akes

T

he

A

natomy

F

inal

V

ery

G

ood

V

acations

A

re

H

(41)

II. Spinal Nerves

A.

Nerves arise from ventral roots and

dorsal roots off of the spinal cord

B.

Dorsal contains sensory neurons

(42)

Spinal Nerves

C.

C. 31 pairs are named and 31 pairs are named and

numbered according to numbered according to what region of the spinal what region of the spinal cord they originate from cord they originate from 1. Cervical Nerves – 8 1. Cervical Nerves – 8 pairs

pairs

2. Thoracic Nerves – 12 2. Thoracic Nerves – 12 pairs

pairs

3. Lumbar Nerves – 5 3. Lumbar Nerves – 5 pairs

pairs

4. Sacralspinal nerves – 5 4. Sacralspinal nerves – 5 pairs

pairs

5. Coccygeal nerves – 1 5. Coccygeal nerves – 1 pair

(43)

D. When a spinal nerve leaves the

vertebral column, it divides into

branches called

rami

.

1. Dorsal – deep muscles and skin of

back

2. Ventral – superficial muscles of

back, structures of limbs, and trunk

E. A network of adjacent nerves is called

plexuses.

All spinal nerves form

plexuses except the thoracic nerves;

they go directly to the muscles and

skin of trunk.

(44)

Plexuses

1.

Cervical – skin and muscles of the

head, neck, shoulders, and

diaphragm (phrenic nerve)

2.

Brachial – upper arms, neck, and

shoulders (carpal tunnel)

a.

Axillary (rotates and abducts arm)

b.

Radial (flexes forearm and extends

fingers)

c.

(45)

Plexuses

3. Lumbar – abdominal wall, external

genitalia, and lower limbs

a. Obturator (rotates and adducts thigh)

b. Femoral ( flexes thigh and extends

leg)

4. Sacral – buttocks and lower limbs

a. Tibial (flexes foot, leg, and toes)

(46)

Functional Nervous System

I.

I. Somatic Nervous SystemSomatic Nervous System

a.

a. Function – transmit action potentials from CNS to Function – transmit action potentials from CNS to

skeletal muscle. skeletal muscle.

(47)

II. Autonomic Nervous System

A.

Function – transmits action potential

from CNS to smooth muscle.

1. Automatic response

2. Receives impulses from ANS and have

(48)

B. In the ANS there are two motor

neurons and a ganglia

1.

The first neuron (

preganglionic

neuron

) which are myelinated, comes

from the CNS and relays to the ganglia.

2.

The second neuron (

postganglionic

neuron

), which are unmyelinated,

comes from the ganglia and delivers an

action potential to the visceral effector

(organ).

3.

Ganglia receive messages and direct to

appropriate postganglionic neuron.

(49)

III. Divisions of Autonomic

A.

Sympathetic

1.

1. Concerned with processes involving Concerned with processes involving expending energy.

expending energy. 2.

2. Contains the parasympathetic system to Contains the parasympathetic system to maintain homeostasis.

maintain homeostasis. 3.

3. Active during times of extreme stress, Active during times of extreme stress, emotion, and exercise.

emotion, and exercise. 4.

4. Fight or Flight response.Fight or Flight response.

a.

a. Pupils dialatePupils dialate

b.

b. Heart rate increase Heart rate increase

c.

(50)

B. Parasympathetic

1.

Concerned with conservation of energy

2.

(51)

(52)

Summary

1.

Stimulus (pin in paw) – Activation of

receptor

2.

Activation of Sensory Neuron

3.

Info processing in CNS

4.

Activation of Motor Neuron