Lecture 1 Flashcards
Which is faster: The nervous system or The endocrine system? Why?
The nervous system, because it uses action potentials which travel through myelinated axons that might reach 120 m/s and unmyelinated axons from 2-5 m/s.
Which has a higher gain: The nervous system or The endocrine system? Why?
The endocrine system, because the hormones try to bring back blood pressure to almost 100 with zero error; the game will be infinite. (Nervous system might bring it back to 105 = -3 gain)
What does the nervous system affect?
Skeletal muscles and glands
What does the endocrine system affect?
Growth, metabolism, and reproduction.
If the signal does not reach the cerebral cortex, what happens?
The signal will not consciously be perceived.
What is the central nervous system (CNS) composed of?
1) Brain
2) Spinal cord
What goes to the CNS from the PNS?
Afferent (Ascending) division:
1) Sensory stimuli
2) Visceral stimuli
What goes out of the CNS to the PNS?
Efferent (descending) division:
1) Somatic nervous system (motor/voluntary)
2) Autonomic nervous system (involuntary)
What senses changes in the environment?
Receptors
Receptors are also called ___, because:
Transducers; They convert any type of energy (action potential).
Receptors attach with what kinds of neurons?
Afferent neurons.
What are tracts?
Collection of axons in the CNS.
What are nerves?
Collection of axons in the PNS.
Where are the cell bodies of afferent neurons found?
In the dorsal root ganglia.
If the signal doesnt ascend, then what connects afferent neurons with efferent neurons?
Interneurons
What are the sensory divisions of the nervous system?
1) Tactile
2) Visual
3) Auditory
4) Olfactory
What are the integrative divisions of the nervous system?
1) Information processing
2) Memory creation
What are the motor divisions of the nervous system?
Respond to and move about in our environment.
What does corticospinal mean?
From the cerbral cortex to the spinal cord.
Where did the signals go to synapse with the motor neurons?
The anterior horn of the spinal cord (alpha motor neuron)
What is an alpha neuron?
Big and myelinated neuron.
What is the muscle tone?
Minimal contraction found in the muscle
What are the 2 paths that signals can take?
1) Sensory -> Interneuron -> Motor
2) Sensory -> ascends CNS (brain) -> motor
Interneurons are responsible for:
1) Integrating afferent information and formulating an efferent response
2) Higher mental functions associated with the mind and memory
Most of the neurons found in the CNS are:
Interneurons
What are the characteristics of interneurons?
1) Small
2) Highly excitable
3) Outnumber other neurons (interneurons > afferent (sensory) > efferent (motor)
What are the types of sensory receptors?
1) Pain and temperature (free nerve endings)
2) Pressure (Pacinian corpuscles)
3) Touch (Meissener’s corpuscle)
4) Muscle (Muscle spindles)
5) Joints (Kinesthetic receptors; proprioceptors)
Where does the sensory division start?
From the sensory receptors
Where does the motor division start?
Cerebral cortex
Which part of the muscle does the motor division go to?
Extrafusal muscle fibers
Where is the primary somatosensory cortex located?
On the postcentral gyrus.
Sensory signals usually stop at the ____, so it is the relay station for almost all sensations except ____.
Thalamus; olfaction.
What are the three levels of CNS function/organization?
1) Spinal cord level
2) Lower brain level
3) Higher brain (Cortical) level
Which level is present in primitive or lower animals?
Only the spinal cord level
What does the spinal cord level contain?
1) Walking circuits
2) Withdrawal circuits
3) Circuits for reflex control of organ function
What do we test when we test the reflexes?
The integrity of the spinal cord
What does the lower brain level contain?
1) Medulla oblongata
2) Pons
3) Midbrain
What does the lower brain level control?
Subconscious body activities:
1) Arterial pressure
2) Respiration
3) Equilibrium
4) Feeding reflexes
5) Emotional patterns
What is the Higher brain (Cortical) level?
1) A large memory storehouse
2) Essential for thought processes
Does the cortex function alone?
No, it always functions in association with lower brain centers.
What is the neuron?
The structural and functional unit of our nervous system
What are the three major components of a neuron?
1) Soma: Body
2) Axon: Extends from Soma to terminal part of effector
3) Dendrite: high resistance projections from the soma to the sensory portion of the neuron
What is the first part of a neuron called?
Axon hillock
What is found at the end of the axon?
Axonal terminals or axonal buttons
What do axonal buttons contain?
Neurotransmitters
Neurons have all the cell organelles except ____.
Centrioles
Why do neurons lack centrioles?
Because they dont divide/regenerate.
Why is the CNS enclosed by bony structures (skull and vertebral column)?
For protection.
What is the function of the cerebrospinal fluid (CSF)?
Shock absorber
Why are dendrites unable to produce action potentials?
Because they have a very low density of sodium voltage gated channels.
Where is the action potential best produced?
Axon hillock (first unmyelinated part of axon)
Which has the highest density of sodium voltage gated channels?
Axon hillock
The CNS is also protected by meninges. What are the three layers from outside to inside?
1) Dura mater
2) Arachnoid mater
3) Pia mater
Which cells produce the myelin sheath in the CNS?
Oligodendrocytes
Which cells produce the myelin sheath in the PNS?
Schwann cells
What are the nodes of Ranvier?
Unmyelinated areas interrupting myelin.
What is the anterior motor neuron?
A kind of neuron that contains many synapses:
1) Axosomtic with soma
2) Axodendritic with dendrites
3) Axoaxonal with axons
What kind of conduction is one-way conduction/synapse?
Chemical conduction/synapse
What kind of conduction is two-way conduction/synapse?
Electrical conduction/synapse
Why is chemical synapse one-way?
Because there are no receptors on the pre-synaptic neuron (only post-synaptic).
Which type of conduction is more common in the CNS?
Chemical synapse (one-way conduction)
