Bioscience year 1- the nervous system

What is the nervous system?

A system which collaborates with the endocrine system and is responsible for co-ordinating all the systems within the body

What does the nervous system do?

Detects and responds to any changes in the external or internal environment to maintain homeostasis

What is more immediate, nervous or endocrine control?

Nervous

What is the sensory function of the nervous system?

To gather information both inside and outside of the body and transmit it to the brain

What is the integration function of the nervous system?

To process the information and make decisions for appropriate responses in the brain and spine

What is the motor function of the nervous system?

To send information to the muscles, glands and organs sos that they can respond appropriately

What are neurones?

Basic functional cells of the nervous system

Where do sensory (afferent) neurones carry impulses?

Towards the CNS from sensory receptors in the external and internal environment

Where do motor (efferent) neurones carry impulses?

From the CNS to the effector organs (effectors)

Neurone structure and their definitions

Dendrite: a structure found on a neurone which receives stimulus and carries impulses toward the cell

Cell body: the part of the neuron which contains the nucleus

Axon: the fibre which carries impulses away from the cell body

Neurone adaptations and their definitions

Myelin sheath: a dense lipid layer which insulates the axon

Nodes of ranvier: gaps in the myelin sheath

Schwann cells: cells which produce myelin in PNS

What are oligodendrocytes?

Cells which produce myelin the central nervous system

What are neuroglia?

Non-conductive cells that support and protect the neurones

What are neurotransmitters?

Chemicals in the junction which allow impulses to be started in the second neurone or an effector (muscle or gland)

What is the brain and how much does it weigh

Large and complex organ (1.5kg)

What is the cranium

The skull which protects the brain from injury

What are the 4 main regions of the brain and its functions

1. Cerebrum- made up of the left and right cerebral hemispheres connected by the corpus callosum

2. Diencephalon- link between the nervous and endocrine system which includes thalamus and hypothalamus

3. Brain stem

4. Cerebellum

What is the corpus callosum

A band of myelinated axons which facilitates inter hemispheric communication

What is the key function of the hypothalamus and thalamus

Hypothalamus- links the nervous system to the endocrine system via the pituitary gland

Thalamus-relays signals to/from the brain and body, including relaying sensory + motor signals to the appropriate region of the cerebral cortex for action

What is the spinal cord and what is made of

An info superhighway that relays messages between the brain and body

Nervous tissue in a thin cylindrical structure

From where to where is the spinal cord situated

Runs through the spinal canal from the brain through a hole in the base of the skull (formed magnum) and ends at the 1st lumbar vertebra

How do nerves leave the spinal cord

In pairs

How many vertebrae (bones) in the spinal column and what are the 5 regions

33 bones

1. Cervical: C1-7

2. Thoracic: T1-T12

3. Lumbar: L1-L5

4. Sacrum: S1-S5

5. Coccyx: C1-C4

What is the brain and spinal cord also protected by

• the meninges

• The blood-brain barrier

• Cerebrospinal fluid

What are the 3 layers of membrane in the meninges

1. Pia mater: the inner layer of the meninges which is intimately attached to the cord/brain

2. Arachnoid mater: middle membrane

3. Dura mater: tough outer membrane

What is the subarachnoid space

A space between the Pia and arachnoid mater which is used for spinal block

What is the epidural space

A space between the dura mater and bone, used for epidural

What is the cerebrospinal fluid (CSF) and what does it carry and remove

A clear fluid that circulates around the brain and spinal cord which act as a shock absorber

Oxygen and nutrients and removes waste such as carbon dioxide

What is the blood brain barrier and what are some important functions

Semi permeable membrane separating blood from cerebrospinal fluid

• Protects the brain from foreign substances in the blood which may cause injury

• Protects the brain from hormones and neurotransmitters in the rest of the body

• Maintains a constant environment for the brain

Why is the neonatal brain vulnerable at term

The blood brain barrier is not fully developed

How may pairs of spinal nerves branch off the spinal cord

31

Where do the name of nerves relate to

The region of the vertebral column from which they originate

What does each spinal nerve contain and how is each spinal nerve connected to the spinal cord

• A mixture of sensory and motor nerves that carry messages between the body and spinal cord to control sensation and movement

• Dorsal root

What does the dorsal root contain

Sensory (afferent) neurones

What does a ventral root contain

Motor (efferent) neurones

What is a dermatome and what does each spinal nerve receive from it

• the area of skin thats suppled by a single spinal nerve

• Sensory info

Where does the pudendal nerve arise from and where does it receive info from

S2-S4

The external genitalia of both sexes and the skin around the anus, anal canal and perineum

When can pudendal nerve block be given

Before instrumental birth, episiotomy and other minor vaginal procedures

What should an ideal labour block cover

Sensory loss from T0- S5 (with initial motor block)

How does the nervous system respond quickly to situations that immediate response

An involuntary reflex action is produced to prevent serious injuries or death- don’t involve brain and completed at spinal cord level

What does the somatic nervous system control

Controls muscles that change position (voluntary)

Autonomic nervous system

• involuntary

• Enteric nervous system: regulates smooth muscle + secretion in the gut

• Parasympathetic: rest + digest

• Sympathetic: flight + fight

What are 2 tools for assessing the level of consciousness

• Glasgow coma scale (eye opening response, verbal response, motor response)

• AVPU

How regularly should an assessment of sensory block level during labour epidural be carried out

Hourly

What is assessed in the client post CS

Return of sensory and motor function

What is assessed during labour epidural

Motor block level

Why should women on magnesium sulphate be monitored

For clinical signs of magnesium toxicity including checking deep tendon reflexes

Common neurological conditions in pregnancy

• migraines

• Multiple sclerosis

• Seizures 1/200

• Sciatica

• Carpal tunnel syndrome

What can increased levels of oestrogen and progesterone due to neurotransmitters?

Affect neurotransmitters leading to changes in emotions and moods which may contribute to developing or exacerbating mental health conditions

What can long term dysregulation lead to?

-pain
- fatigue
- sleep disturbance
- anxiety
- burnout
- depression

What techniques may help regulation of the nervous system?

- mindfulness
- affirmations
- relaxations
- breathing exercises
- mindful movement