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