The structure of the nervous system

In a nutshell

The nervous system controls all of the bodies processes from hormones to movement. Different areas of the brain control different aspects of these processes.

Central nervous system (CNS)

The CNS consists of the brain and spinal cord.

Spinal cord

The spinal cord has a cylindrical structure. A "canal" runs through the centre of the spinal cord filled with cerebrospinal fluid. The cord itself is made up of grey matter on the inside and white matter on the outside. The spinal cord primarily transmits instructions of receptors to effectors.

Grey matter	Nervous tissue comprised mainly of cell bodies of neurones.
white matter	Nervous tissue comprised mainly of axons and myelin sheaths.

Vertebrae

The vertebrae of the backbone protect the spinal cord. There is a gap between each vertebrae where two "offshoots" from the spinal cord called spinal nerves leave. The pair of spinal nerves travel to different sides of the body.

Biology; Control systems; KS5 Year 12; The structure of the nervous system — 1. White matter, 2. Grey matter, 3. Spinal nerves, 4. Central canal

The brain

The brain receives stimuli and information from all over the body, it then analyses these stimuli and produces a response.

1. Frontal lobe, 2. Parietal lobe, 3. Occipital lobe, 4. Temporal lobe, 5. Olfactory area, 6. Cerebellum, 7. Medulla oblongata

1. Hypothalamus, 2. Pituitary gland, 3. Medulla oblongata, 4. Cerebellum, 5. Cerebral hemispheres

Part of the brain	location	function
Medulla oblongata	The medulla oblongata is located at the bottom of the hindbrain. It is essentially a continuation of the top part of the spinal cord and links the brain and spinal cord.	The medulla oblongata contains hubs which control the force and rate of heart beats. It also regulates the diameter of blood vessels controlling blood pressure. Another hub of the medulla oblongata controls the rate of breathing. Curiosity: In the medulla the ascending and descending pathways of the spinal cord flip around. This means the right side of your brain controls the left side of your body and vice versa.
Cerebellum	The cerebellum is located in the hindbrain. It has an outside layer of grey matter.	The cerebellum is responsible for controlling involuntary movement. Although it does not initiate movement directly it helps out the coordination of the movement. Removal of the cerebellum results in clumsy movements.
Cerebrum	The cerebrum is made up of two cerebral hemispheres. They make up the majority of the human brain.	Coordination of voluntary and involuntary movement is overseen by the cerebrum. The cerebrum contains folds which increase the surface area. The cerebrum has a layer of grey matter $3\space mm$ thick packed with non-myelinated neurones. The collection of folds is called the cerebral cortex. Each hemisphere of the cerebral cortex collects and processes information. Then the hemispheres coordinate movement and responses in reaction to the information.
Basal ganglia	Basal ganglia are made up of separate groups of neurones and are found in each hemisphere of the cerebral cortex. Both hemispheres of the cerebral cortex are made up of four lobes called frontal, parietal, temporal and occipital.	The basal ganglia process information and relays instructions to the cerebral cortex, thalamus and hypothalamus. They are also responsible for involuntary skeletal muscle tone and movement. The basal ganglia receive information and relay complex responses. Memory is applied to the responses. A range of complex mental processes take place to pick the best response.
Hypothalamus	The hypothalamus is found at the bottom of the forebrain. The brain is extremely well supplied with blood vessels, however, the hypothalamus compared to other parts of the brain is especially well supplied with blood vessels.	The hypothalamus controls the autonomic nervous system (ANS). Osmoregulation is controlled by the hypothalamus which involves the constant monitoring of sugars, amino acids and ions. Furthermore, the hypothalamus controls body temperature and drinking reflexes.

Peripheral nervous system (PNS)

The PNS is made up of axons and dendrons (nerve fibres) organised into bundles. Connective tissue sheaths protect the bundles and keep them separate.

The nerve fibres in the PNS are made up of sensory neurones which transport impulses to the CNS and motor neurones which transport impulses to glands and muscles. The PNS controls voluntary movement through motor neurones.

Autonomic nervous system (ANS)

The ANS controls mainly involuntary actions inside the body. The ANS is made up of motor neurones that transmit information to the smooth muscle of the organs and to glands.

There are two parts of the ANS called the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS).

Sns

pns

Active in periods of stress. Control of "fight or flight" response.

Example

Induces adrenaline release in stressful situations.

Active in periods of rest. Control of conservation of energy and body reserves.

Example

Decreases heart rate whilst resting.

Noradrenaline neurotransmitter is used.

Acetylcholine neurotransmitter is used.