Nervous System (copy)

Structure of the nervous system

Structure of the nervous system

Central Nervous System

• Functions as a coordination centre which processes information

• consist of brain and the spinal cord

Peripheral Nervous System

is that part of your nervous system that lies outside your brain and spinal cord. It plays key role in both sending information from different areas of your body back to your brain, as well as carrying out commands from your brain to various parts of your body.

Structure of a Nerve

organ consisting of a bundle of nerve fibres enclosed in a sheath of connective tissue. Each nerve cell consists of the cell body, which includes the nucleus, a major branching fiber (axon) and numerous smaller branching fibers (dendrites).

Basic Structure of a neurone

cell body, axon, dendrons

Structure of cell body

Contains nucleus, cytoplasm and organelles such as mitochondria

Function of Dendron + Dendrites

Transmits nerve impulses to the cell body

The end branches of dendron are called dendrites which receive signals from other neurons

Function of Axon + Axon Terminal

Transmits nerve impulses away from the cell body

The ends of the axon are called axon terminals which transmits nerve impulses to the effectors

Function of Myelin sheath

Insulates nerve fibre and increases speed of transmission of nerve impulses.

What are Nodes of Ranvier?

regions where myelin sheath is absent

Synapse

gap or junction between neurons, or between neuron and effector.

What happens when nerve impulses reach the axon terminal?

When nerve impulses reach the axon terminals, a chemical, neurotransmitter, diffuses in small vacuoles to the presynaptic membrane where it is released into the synaptic cleft. the neurotransmitters then meet the post synaptic membrane which the receptor cells on it. when the neurotransmitters then meet with them the impulse will be carried through to the next Nerone

Structure + Function of Sensory Neuron

Circular cell body with long dendron and short axon

Cell body and dendrites are outside the CNS and the axon is inside the CNS

Function: Sensory Neurons transmits nerve impulses from receptors to the CNS

Structure + Function of Relay Neuron

Can have an irregular cell body

Whole neuron is found inside the CNS

Function:

• transmits nerve impulses from sensory to motor neurons.

• transmit nerve impulses to other relay neurons in the CNS

Structure + Function of Motor Neuron

Irregular cell body with dendrites and long axon

cell body and dendrites are in the CNS and the axon is outside the CNS

Function: transmit nerve impulses from the CNS to the effectors

Parts of the brain

Forebrain, Midbrain, Hindbrain

What is a reflex?

immediate response to a specific stimulus that occurs without any conscious effort

A reflex arc includes:

• Receptor - nerve tissue or sense organ

• Sensory neuron, Relay neuron in the reflex centre (spinal cord/brain), motor neuron

• Effector- muscle or gland stimulated to respond appropriately

Types of simple reflexes:

Spinal reflex action: the reflex centre is in the spinal cord

Cranial reflex action: the reflex centre is in the brain

What happens during a withdrawal reflex? (ESSAY QN)

1. When a stimulus stimulates the pain receptor on the finger, nerve impulses are generated

2. Nerve impulses travel along the sensory neurone to the spinal cord

3. In the spinal cord, neurotransmitters are released across the synapse between the sensory and the relay neurone

4. The nerve impulse flow along the relay neuron and neurotransmitters are released across the synapse to the motor neurone

5. Nerve impulses leave the spinal chord along the motor neurone to the effector. The effector is the bicep muscle, which contracts to cause the withdrawal action