2.8. Nervous System Flashcards
What is the nervous system comprised of?
Millions of neurons and glial cells
What makes up the nervous system?
Brain, spinal cord (Central Nervous System)
Nerves (Peripheral Nervous System)
What is the VOLUNTARY system of peripheral nerves called?
Somatic nervous system
What is the INVOLUNTARY system of peripheral nerves called?
Visceral nervous system
later turns into the sympathetic and parasympathetic
What do glial cells provide?
Nourishment and support to the neurons
Neurons are so specialised they do not undergo further mitotic divisions once developed.
What does this mean in the neonatal period?
Number of neurons produced far exceeds the level required
What is the purpose of a DENDRITE?
Branch-like structures extending away from the cell body, and their job is to receive messages from other neurons and allow messages to travel to the cell body.
What is the CELL BODY?
Contains nucleus, smooth & rough ER, golgi apparatus, mitochondria etc
What is the AXON?
Carries an electrical impulse from the cell body to axon terminals, which can then pass the impulse to another neuron
What is the SYNAPSE?
Chemical junction between axon terminals of one neuron and dendrites of the next
What is the MYELIN SHEATH?
Acts as insulation to minimise dissipation of electrical signal as it travels down the axon.
Greatly increases speed of conduction
What is the NODE OF RANVIER?
Periodic gaps in the myelin sheath where the signal is recharged
What are the 3 major types of neuron?
Sensory/ Afferent
Motor/ Efferent
Interneurons
Describe a sensory/afferent neuron
Converts external stimuli from environment to corresponding internal stimuli
Describe a motor/efferent neuron
Project axons outside of the CNS to directly or indirectly control muscles
Describe an interneuron
‘middle men’ that form connections between the other 2 types
Describe the process of communication among neurons
- Neurons usually have a negative conc grad- more Na+ outside, more K+ inside (resting membrane potential)
- When the electrical impulse reaches the axon, Na gates open, allowing Na+ across the conc grad into the axon
- This causes the membrane to become depolarised
- Na channels close, membrane becomes leaky to K+, which move out of the axon down the electrochemical gradient
- Results in repolarisation
- Process propagates along length of neuron (action potential)
- Neurotransmitters are released from the first neuron at synapse
- They travel across and trigger an action potential in the second neuron
- If the axon has a myelin sheath, action potential moves faster
What is a synapse?
A junction between the presynaptic cell and the postsynaptic cell
What are the 2 types of reaction that occur at the synapse?
- Chemical
2. Electrical
What are the 3 parts of the HINDBRAIN?
- Pons
- Medulla
- Cerebellum
Key functions of PONS
Regulates body temperature, heart rate, swallowing, breathing
Key functions of MEDULLA
Control centre for respiratory, cardiovascular, digestive systems
Key functions of CEREBELLUM
Coordinates skeletal muscles to produce smooth motions
Key functions of MIDBRAIN
Motor movement- eye, auditory, visual processing
What are the 2 parts of the DIANCEPHALON?
- Thalamus
2. Hypothalamus
Key functions of THALAMUS
Passes information to the cerebral cortex
Key functions of HYPOTHALAMUS
Sexual behaviour, release hormones, regulate body temp, controls appetite, regulates emotional responses
Key function of SPINAL CORD
Convey info to brain, carry info to skeletal muscles, control posture, control nearby organs
Key functions of CEREBRUM
Thought and control centre, emotions and decision making.
Gray matter- mass of cell bodies, synapses, dendrites
White matter- myelin-coated axons
What are the 4 parts of the CEREBRAL CORTEX?
- Frontal lobe
- Temporal lobe
- Occipital lobe
- Parietal lobe
Starting at the TOP of the spinal cord, label the 4 groups of nerves
- Cervical nerves
- Thoracic nerves
- Lumbar nerves
- Sacral and Coccygeal nerves
What is the significance of Sacral and Coccygeal nerves in midwifery?
- Nerves of pelvic organs and lower limbs
- Sensory innervation of perineum and anal sphincters
^^EPIDURAL affects these nerves^^
What is the DURA?
Outermost layer of spinal cord tissue
Tough protective coating
What is the epidural space filled with and where is it located?
- Filled with adipose tissue and contains a network of blood vessels
- Located between the dura matter and surrounding bone of the vertebrae
List 3 changes or symptoms which pregnant women may experience during pregnancy as a result of changes to the CNS
- Grey matter volume shrinks during pregnancy and for up to 2 years post birth
- Pituitary gland enlarges gradually. In 3rd trimester, oedema can affect vision
- Progesterone affects neural activity in the brain, reducing level of excitatory neurotransmitters- increased desire for sleep (1st trimester)
What makes up the PNS (peripheral)?
All neural structures outside the brain and spinal cord- Peripheral nerves and associated ganglia and efferent motor endings
What does the PNS do?
Detects changes in the body’s external or internal environments
What is the somatic nervous system subdivided into?
- Sensory components
2. Motor components
What is the motor component responsible for?
Voluntary movement
Gate Control Theory asserts that activation of nerves which do not transmit pain signals (non-nociceptive fibres) can interfere with signals from pain fibres, thereby inhibiting pain.
How could this theory be used to advise women on pain management strategies during labour?
- TENS (Transcutaneous electrical nerve stimulation) machine -> overstimulates nerves
- Massage
- Heat pads
What is a neuromuscular junction?
A chemical synapse formed by the contact between a motor neuron and a muscle fibre
What is the reflex arc?
Reflexes occur over specific neural paths called reflex arcs and may be somatic or autonomic. Many reflexes occur with little or no brain input.
What are the 5 components of the reflex arc?
- Receptor
- Sensory neuron
- Integration centre
- Motor neuron
- Effector
What is a RECEPTOR?
Specialised part of a neuron that receives a signal
What is a SENSORY NEURON?
Transmits the signal to the spinal cord
What is the INTEGRATION CENTRE?
An interneuron in the spinal cord that connects input to output
What is a MOTOR NEURON?
transmits the signal to the effector
What is the EFFECTOR?
the tissue that turns the signal to action (muscle)
