principles of nervous system 1 Flashcards
What is a neuron?
functional unit of the nervous system
What are neuroglia?
support neurons
What are the 5 parts of a neuron?
- soma/cell body
- dendrites
- axon hillock
- axon/nerve fibre
- axon terminals
Describe the soma/cell body of a neuron
- contains nucleus
- synthesis of proteins (lots of ER)
- cellular metabolism (lots of mitochondria)
Describe the dendrites of a neuron
- receives inputs
- convey info towards soma
- large SA (spines) for synapse formation
Describe the axon hillock of a neuron
- origin of the axon
- very excitable
Describe the axon/nerve fibre of a neuron
- transmits action potential
- usually only one (althoug may branch)
Describe the axon terminals of a neuron
- synpase on other neurons/effector organs
- may form specialised sensory endings
What is a unipolar neuron?
- one axon only
- we have pseudounipolar
Give examples of pseudounipolar neurons?
- primary sensor neurons
Where are the cell bodies of our pseudounipolar neurons found?
dorsal root ganglia
What is a bipolar neuron?
one axon and one dendrite
Give examples of bipolar neurons
- specialised sensory neurons
- found in retina, olfactory epithelia
What are multipolar neurons?
one axon and multiple dendrites
Give examples of multipolar neurons
- majority of neurons in brain
- motor neurons
- autonomic ganglia
How big usually are myelinated axons?
1-10 micrometers diameter
How big usually are unmyelinated axons?
under 1 micrometer diameter
What are 3 types of neuroglia?
- astrocytes
- oligodendrocyte
- microglia
What are the functions of astrocytes?
- structural support
- scaffold for neurons during development
- supply nutrients
- maintain ionic gradients
- neurotransmitter uptake
- repair of nervous system
- form barrier around vessels
What do oligodendrocytes do?
myelinates axons
What do microglia do?
act as immune cells
- secrete cytokines
- phagocytic
- cytotoxic
promote repair
What are the neuroglia of the peripheral nervous system (PNS)
schwann cells
What are the functions of schwann cells?
- myelinate axons
- secrete cytokines, phagoytic
- regeneration (provide substrate for axon to grow along)
What constitutes the central nervous system?
- brain
- spinal cord
What constitutes the peripheral nervous sytem?
communication between CNS and periphery
What is the most superior part of the brain called?
dorsal surface
What is the brain divided into?
- forebrain
- midbrain
- hindbrain
What is grey matter in the brain?
- neuronal cell bodies
- synapses
- dendrites
What is white matter in the brain?
myelinated axons
What makes up the forebrain?
- cerebral hemispheres
- thalamus
- hypothalamus
What makes up the hindbrain?
- pons
- medulla
- cerebellum
Describe the cerebral hemispheres
- outer grey matter is cerebral cortex
- 10-20 billion neurons
- 2.5mm thick
- divided into lobes
What are the functions of the cerebral hemispheres?
- processing motor and sensory information (20%)
- cognition (80%)
Describe the thalamus
- relay centre of brain
- paired structure
- centrally located
- sensory info passes via thalamus before reaching cortex
Describe the hypothalamus
- important in homeostasis
- sits below thalamus
- controls autonomic and endocrine nervous systems
What is the brainstem formed by?
midbrain and hindbrain
What does the brainstem do?
- connects cortex to spinal cord
- controls respiration and cardiovascular systems
What does the cerebellum do?
coordinate muscular activity
Where does the spinal cord start and go to?
from atlas (C1) to first/second lumbar vertebra (L1-L2)
Where does the spinal cord sit?
within vertebral canal
What are the functions of the spinal cord?
- conveys info
- involved in reflexes
What are the segments of the spinal cord called from top to bottom?
- cervical
- thoracic
- lumbar
- sacral
Describe the spinal cords anatomy
- inner core of grey matter
- outer white matter
- efferent axons exit ventrally
- afferent axons enter dorsally
(via peripheral nerves)
How are axons organised?
into fascicles
What are the layers of axons from outside to in?
- epineurium
- perineurium
- endoneurium
What are the two components of the peripheral nervous system?
- somatic (voluntary)
- autonomic (involuntary)
What does the somatic component of the nervous system supply?
- skeletal muscles
- sensory from skin, muscles and joints
What does the autonomic component of the nervous system supply?
- viscera
- smooth muscle
- glands and vessels
Where do all peripheral nerves arise from?
- brain or brainstem as cranial nerves
- spinal cord as spinal nerves
What do spinal nerves provide?
- motor supply
- sensory (somatic) supply
- sympathetic (autonomic) supply
