Nervous system

Central nervous system

Brain and spinal cord.

Peripheral nervous system

All other nerves in the body. They feed into the CNS.

CNS- The Brain

Cranium (skull)

Protection

Meninges membrane (3 layers)

Protection

What is the Infection of the meninges by bacteria or viruses called?

Meningitis

Cerebrofluid (between meninges)

Protection

Cerebrum (largest part of brain)

Voluntary movement, memory, speech and language, learning and intelligence, hearing

Hypothalamus

Maintains a constant internal environment in the body including thirst, hunger, water balance, body temp.

Pituitary gland

Produces hormones including ADH, TSH, FSH and LH.

Cerebellum (connected to ear)

Co-ordinates movement and balance as well as hand-eye co-ordination.

Medulla oblongata

Controls involuntary movement including breathing, heart rate, swallowing.

Neuron

A single nerve cell.

CNS- Spinal Chord

Mechanism of reflex action/arc

1. Electrical message carried to spinal cord via sensory neuron.

2. Enters spinal cord via dorsal root ganglion (one-way door in).

3. Converted into a motor neuron via the interneuron located inside spinal cord. Message passed out of spinal cord on the motor neuron via ventral root (one-way door out).

4. Message carried to muscle where reaction occurs.

1.

Electrical message carried to spinal cord via sensory neuron.

2.

Enters spinal cord via dorsal root ganglion (one-way door in).

3.

Converted into a motor neuron via the interneuron located inside spinal cord.

4.

Message passed out of spinal cord on the motor neuron via ventral root (one-way door out).

5.

Message carried to muscle where reaction occurs.

Central canal

Centre of the spinal chord is called the central canal and contains cerebrospinal fluid.

Grey matter

The dark grey area that surrounds the central canal is called grey matter and is composed of cell bodies.

White matter

The white area outside of the grey matter is called white matter and is composed of axons.

Nerves

Carry messages around the human body in the form of electrical impulses known as ions.

Nerves are made up of many nerve cells called neurons (need to know structure of neuron) in close proximity but not touching.

3 types of nerve cells/neurons

1. Sensory neurons

2. Motor neurons

3. Inter neurons

Sensory neurons

Carry electrical messages (ions) to the Central Nervous System from Peripheral Nervous System.

Motor neurons

Carry electrical messages away from Central Nervous System to Peripheral Nervous System.

Inter neurons

Convert sensory messages to motor messages in the brain/spinal cord. Remember: sensory and motor neurons can be found in peripheral nervous system but interneurons can only be found in central nervous system.

Structure of a neuron and the functions of each part

Dendrite

Located at one end of neuron. Picks up electrical impulse from axon of previous nerve cell.

Cell body

Contains a nucleus and controls activities of the neuron. Produces neurotransmitters that then travel to neurotransmitter swellings where they are stored before being released into synaptic cleft.

Schwann cell

Produce the myelin sheath.

Myelin Sheath

Myelin sheath is produced by Schwann cells and is composed of lipids. This layer (or sheath) is wrapped around the axon. It acts as an insulator and speed up the rate of transmission of the electrical impulse.

Axon

Carries electrical impulse along nerve.

Neurotransmitter swellings

Found at end of axon (at axon terminal), stores and secretes neurotransmitters into synaptic cleft.

Synaptic cleft

Gap between axon of one neuron and dendrite of another neuron.

Synapse

Region including axon terminal of one neuron and dendrite of another neuron.

Neurotransmitter

Chemical produced to carry electrical impulse across synaptic cleft gap. Produced in the cell body but stored in neurotransmitter swellings. Examples include dopamine, acetylcholine and noradrenalin.

In which direction does the electrical impulse (in the form of ions) travel in the neuron (nerve cell)?

Electrical impulse always travels in the direction from dendrite to axon terminal.

Motor neuron

Similar to the structure of sensory neuron and various parts have the same function. However, the cell body is located in the centre of the neuron in a sensory neuron but next to the dendrite in a motor neuron.

What is the Deficiency disease of the nervous system?

Parkinson’s disease

Symptoms

Cause

Prevention

Treatment

Symptoms: Hand tremors, muscle contraction that cannot be controlled

Cause: Failure to produce neurotransmitter dopamine

Prevention: None

Treatment: Medication that mimics dopamine or produces dopamine (L-dopa), physiotherapy and gentle exercise

Differences between nerves(nervous system) and hormones(endocrine system)