Nervous System - grade 12

The reflex arc

-Happens in less than a

second - information has

not even travelled to the

brain

.-When it does, the sensation of

pain will become noticeable and you

may scream!

-If you had to wait to feel the pain first - the burn

would be a lot

worse

.

What do the somatic nerves consist of (PNS)

1. To/from skeletal muscle,

bones and skin

2.sensory and motor somatic nerves

What are the divisions the vertebrate nervous system

1. Central Nervous DIVISIONS of the Vertebrate

Nervous System

2. Peripheral Nervous System

(PNS)

What composes the CNS?

1.nerves, brain, spinal cord

2.coordinating centre

What composes the Peripheral Nervous System

(PNS)

1.Somatic Nerves

2.Autonomic Nerves

autonomic nervous system (PNS)

special motor nerves that

control the internal organs

sympathetic nervous system

and parasympathetic nervous system

What do the nervous system cells consist of

Neurons - cells that conduct nerve impulses

(functional unit).

Nerve: is a bundle of many neurons

Glial cells (neuroglial cells):structural

support and metabolism of nerve cells (

do not conduct)

Neuron Anatomy -Diagram

Neuron Anatomy: Cell Body

Nucleus and majority of cytoplasm

Neuron Anatomy: Dendrites

projections of cytoplasm that

carry impulses TOWARD the

cell body

Neuron Anatomy: Axon

extension of cytoplasm that carries

nerve impulses AWAY from the cell body

Neuron Anotomy -Myelin Sheath

Insulated covering (fatty protein)

over the axon of some nerves,

"myelinated" prevents loss of charge

Neuron Anotomy -Schwann cells

type of glial cell that produces myelin sheath

Neuron Anotomy - nodes of Ranvier

regularly occurring gaps between

sections of the myelin sheath

nerve impulses " jump " from one node to another -increases speed of the impulse

axon diameter also effects speed;narrower

= faster.

Neuron Anatomy: Neurilema

PNS axons (myelinated or unmyelinated)

have a thin membrane surrounding the axon.

Promotes regeneration of damaged axons

Which nervous system can regenerate

The PNS has greater ability to

regenerate than the CNS (spinal cord injuries).

Neurons without myelin sheath or neurilemma do

not regenerate,damage is permanent

. (“greymatter” in brain and spinal cord; white matter has myelin sheath).

Presence of a growth inhibitor in the CNS. Scientists

are looking for ways around this (stem cells

Types of Neurons: Sensory

Sensory Neurons: (afferent neurons)

carry impulses from sensory receptors to

the CNS

Sensory receptors examples:

photoreceptors in eyes (light),

chemoreceptors in nose and skin

(chemicals),thermoreceptors in skin,

hypothalamus (heat/cold).

Types of Neurons -Ganglion

Ganglia -(singular - ganglion):clusters

of sensory nerve cell bodies located

outside of the CNS.

Types of Neurons - Motor Neurons

(efferent neurons)

carry impulses from the CNS to effectors

(muscles, organs,glands...i.e. Things that

produce a response)

Type of Neurons: Interneron

link neurons within the body (found mostly

in the CNS ).

THE REFLEX ARC

-Neural circuit through the spinal cord

that provides a framework for a

reflex action.

-Simplest nerve pathway.

Involuntary,unconscious

Ex. Accidentally touching a hot

stove

Heat detected by thermoreceptors

in skin

2.nerve impulse carried by a sensory

neuron to the spinal cord

3.interneuron in spinal cord passes the impulse to a

motor neuron

4.motor neuron carries impulse to

muscles in arm /hand

5.causes the muscles to contract

and pull hand away