Nervous System 1 - CNS Flashcards
What is the central nervous system ?
- brain and spinal cord
What is the peripheral nervous system ?
- afferent nerves = sensory neurons - messages from periphery to spinal cord (arrive)
- efferent = motor neurons - messages from spinal cord to muscles / glands (exit)
What is motor division of the PNS divided into ?
- autonomic nervous system = involuntary
- somatic nervous system = voluntary
What is the myelin sheath ?
- protective layer that wraps around the axon
- aid in insulating axon
What is the role of Oligodendrocytes in the CNS ?
- produce myelin
- facilitate transmission
What is the role of Schwann cells in the PNS ?
- produce myelin
- facilitate transmission summarise
What are the roles of Astrocytes ?
- enable homeostasis
- Physical barrier/connector
- Reuptake of neurotransmitters
- Support neurons
What is the role of microglia ?
- immune cells of the brain
- phagocytose dead cells and debris
What is the role of ependymal cells ?
- generate the blood-brain barrier
- source of neural stem cells
What is the role of satellite cells in PNS ?
- support cell bodies
- similar to ependymal in CNS
Structure of a neuron ?
• Cell body (soma): control centre
• Dendrite = short, branched extension of a
nerve cell, impulses received from other cells at the synapsis and transmitted to the cell body
• Axons originate at axonal hillock
- Axon terminals – communicate with other neurones / muscles
• axon allows material to be transported from cell body to
axon terminal (and back)
• synapse =where axon terminal meets target cell
What are the 3 functional types of neurons ?
• Peripheral Nervous system
(1) Afferent or Sensory neurons (sense) signals from the periphery to CNS
(2) Efferent neurons = Motor neurons (respond) : signals from the CNS to the muscles/skin etc
• Central Nervous System
(3) Interneurons (integrate) connecting
brain and spinal cord
What are the morphological types of neurons ?
• Bipolar (interneuron) - 2 axons
• Unipolar (sensory) - only one long axon , cell body in middle
• Multipolar (motor) - many dendrites
• Pyrimidal - small soma
What is a nerve ?
- is a bundle of fibres that conduct impulses
between the brain or spinal cord and another part
of the body. - Nerves include fragments of neurons
(axons) and non-neuronal cells (neuroglia)
What is membrane potential ?
- is the difference in electrical charge between
the inside and the outside of the neuron
• Is fundamental to all cells
• Is a result of ion gradients - -70mV
What is a nerve impulse ?
- changes in membrane potential that travel down nerves
Why is the cell membrane important in bioelectricity?
- highly impermeable to ions
- maintaining ion gradients essential for electrical signaling, such as the transmission of nerve impulses.
What are excitable cells ?
- membrane potential changes in response to stimuli
- eg. Neurons
What causes negative membrane potential in neurons ?
- 2K+ in and 3Na+ actively pumped out
- Ca2+ pumped out
- inside more negative
What directions do action potentials travel in ?
- in one direction
- from dendrites to axon
What does the action potential change the membrane potential to ?
+ 30 mV
Why is an action potential described as all or nothing ?
- only occurs if threshold is reached
What is required for an action potential to occur ?
- stimulus has to be strong enough to reach threshold potential
How is an action potential propagated down the axon ?
- the action potential is propagated by voltage-sensitive sodium channels that open due to local changes in membrane potential.
Why can the action potential only move in one direction?
- Na+ channels behind the action potential become inactive
- preventing the signal from moving backward and ensuring one-direction
- also due to refractory period
- area behind becomes hyperpolarised (too negative)
What are the 2 types of synapses ?
- Excitatory: Stimulus (AP) in second neurone, activate neurone number 2
- eg. Glutamate causes depolarisation
• Inhibitory: Stimulus in 1st makes an AP less likely to occur, inhibit neurone number 2
-eg. GABA causes hyper polarisation
What is summation ?
- combination of graded potentials in the post-synaptic neuron
What are the functions of the cerebrum?
- higher functions
- such as thinking, memory, and decision-making.
What functions are controlled by the brainstem ?
- controls involuntary functions like blood pressure, breathing, vomiting, and sleep/arousal.
What are the parts of the brainstem?
- midbrain
- pons
- medulla.
What does the cerebellum control?
- cerebellum coordinates balance and movement.
What is the role of the diencephalon?
- homeostasis
- lies between the brainstem and cerebrum.
What structures are part of the diencephalon?
- thalamus
- hypothalamus
- pineal gland.
What are the functions of the 4 lobes ?
- frontal = speech, problem solving, movement
- parietal = sensory info
- occipital = visual
- temporal = audio
What are the sub-cortical structures of the cerebrum?
• Basal ganglia: Motor control
• Limbic system: A and H
• Amygdala: Emotion and memory
• Hippocampus: Learning and memory (under temporal lobe)
4 regions of spinal cord ?
- Cervical
- Thoracic
- Lumbar
- Sacral
How do sensory and motor nerves enter and exit the spinal cord?
• Sensory nerves enter via the dorsal root.
• Motor nerves leave via the ventral root.
