Nervous sytsem DR/Hanaa

Main Function:

Communication system controls and coordinates functions throughout the body and responds to internal and

external stimuli.

.

Physiological functions• Governs the functions of the body

• Control over muscles, glands, and organs

• Controls heartbeat, breathing, digestion,

and urination

• Regulate blood flow , concentration of

chemicals in the blood.

• Maintaining homeostasis

• Formation of ideas

.

.

Central and Peripheral Nervous Systems

Consists of: brain, spinal cord and nerves

brain

Spinal Cord

Cerebellum

Cerebrum

Medulla Oblongata

Consists of: Brain and Spinal Cord

Central nervous system (CNS)

• Brain and spinal cord

• Housed in the skull and vertebral column

• Three layers ( meninges) ,surround the

brain and spinal cord (Pia matter,

Arechenoids and Dura matter).

• The space between middle and inner

layer is filled with cerebrospinal fluid

(CSF).

Includes all sensory

and motor nerves

Somatic division

(Motor function)

autonomic division

(visceral function)

peripheral nervous system (PNS).

Somatic and autonomic.

• Somatic nervous system controls voluntary

functions of the body, such as the muscle

contractions that cause the limbs to move

• Autonomic nervous system controls the rest of

the involuntary functions such as heart rate and

breathing, digestion and body temperature

regulation

• Parasympathetic:Housekeeping tasks

• Sympathetic: Fight or escape

•

• 12 cranial nerves & 31 spinal nerves.

• Carry two types of information:

(1) sensory impulses traveling to the

CNS from sensory receptors in the

body

(2) motor impulses traveling away

from the CNS to muscles and glands.

A nerve is an organ

containing a bundle

of nerve cells called

neurons.

Neurons carry

electrical messages

called impulses

throughout the

body. Picture shows hundreds of

neuron axons

cell

body

muscle

tissue

TYPICAL MOTOR

NEURON

Axon

dendrite

synapse

cell body

Parts of a Neuron

Axon: long projection that carries impulses away from cell body

1

32

Dendrites: projections that bring impulses into the neuron to the cell body.

Cell body: contains nucleus & most of the cytoplasm

Sensory Neuron

Interneuron

Motor Neuron

Sensory Neuron

Interneuron

Motor Neuron

Muscle Contracts

Synapse

Synapse

Synapse

Sensory Neuron

carry impulses from sense organs to

spinal cord & brain

Interneuron

-processes impulses

in brain and spinal

cord

- connect sensory and

motor neurons

Motor Neurons

carry impulses from the

brain & spinal cord to

muscles & glands

Axon End

Axons branching out

to muscle fibers

According to the structure

unipolar

bipolar

multipolar

.

Neurotransmitters

Synapse (gap)

The message

is transferred

when

RECEPTORSreceive neurotrans-mitters.

(pink

spheres)

Nerve Cell Impulses: •Flow of ions across the plasma membranes

(force drive sodium & potassium ions from one side to the other)** Tiny electrodes on the outside and inside of the plasma membrane**Potential difference (- 70 millivolts)resting P. **Plasma membrane is positively charged on the out side and negatively charged on the inside.** Sodium ions are found in greater concentration outside ,potassium ions are found in greater concentration inside the cell.

Action Potential

Neuron stimulated sudden membrane permeability protein pores open sodium flow in.

(1) upswing, depolarization(voltage goes from -70 millivolts to +30)

(2) downswing, repolarization, the return to the resting potential.

** Increases cell permeability, resulting in a

change in the resting potential

** Protein pores in the plasma membrane open.** Sodium ions flow into the cell through the pores.

** Shift in the resting potential from-70 to +30 (depolarization).** After depolarization, the membrane

returns to its previous state(repolarization) : (1) a sudden decrease in the membrane’s

permeability to sodium (stops the influx of sodium

(2) a rapid outflow of potassium ions

Synaptic Transmission:

• .A synapse consists of

• (1) a terminal (presynaptic neuron)

• (2) a gap (synaptic cleft)

• (3) the membrane of the

• dendrite or postsynaptic cell

• Rapid influx of calcium ions into the bouton from the

extracellular fluid

• Calcium stimulate the release of a chemical substance

stored (neurotransmitters) into the synaptic cleft

• Bind to receptors in the plasma membrane of the

postsynaptic neuron

• Rapid increase in the permeability of the membrane of

the postsynaptic cell to sodium ions.

• Nerve impulse travels down the new nerve cell

Reflex Arc

• Nerves work together with muscles for movement.

• An impulse begins when one neuron is stimulated by

another neuron or by the sense organs.

• The impulse travels down the axons of Sensory

neurons to the brain cells called Interneurons.

• The brain will then send an impulse through motor

neurons to the necessary muscle or organs, telling it

to contract.

وآخر دعواهم ان الحمد هلل رب العالمين