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Lecture 6

BIOL 1F25 Lecture Notes - Lecture 6: Patellar Reflex, Dorsal Root Of Spinal Nerve, Motor Neuron


Department
Biological Sciences
Course Code
BIOL 1F25
Professor
Alan Castle
Lecture
6

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Lecture 6 BIO 1F25 -September 29,2015
-Tapping below patella, pulls on tendon and stretches muscle reflex contraction
of quad muscle, axon branch comes out and splits into two directions carrying
action potential without this the message would decay and not go to the spinal
cord. However, the flow of info down the axon is in one direction, instead of info
going first to cell body then axon it just goes straight to the axon.
-Calcium is released, which triggers for the chemical to be released
-Action potentials go all the way down to the muscle fibres, carried back to quad
muscle where acetylcholine is released, excited muscle and cause contraction
-Cannot contract two leg muscles at the same time, one must relax and lengthen
Sensory neuron: carry info into the nervous system (enter dorsal root),
Motor neuron: cause contractions, hamstring must relax for quad to
contract
Interneuron: original signal responsible for both contraction and relaxation
Knee jerk reflex: monosynaptic circuit (1 synapse) (sensory/motoneruons are
directly connected)
Most spinal reflexes are polysynaptic (more than 1 synapse)
-The brain can also modify reflex networks
Plantar Reflex: stroke foot- normal response is downward response (curing in of
toes)
Babinski response: upward with fanning of toes. Seem in infants (up to 2 years
old)
^^^ When u sticks out a finger and the baby grabs your hand
This reflex doesn’t really disappear; the cortical networks start to inhibit the
reflex. However, that infant reflex can reappear if the cortical networks get
interrupted (brain trauma, disease, etc)
Infant reflex: hidden as we age (inhibited by cortex) but can be unmasked by
brain trauma, some diseases of the nervous system (or excessive alcohol)!
In summary: 4 general features of the nervous system:
1. Stereotyped electrical signals (action potentials)
2. Connections (chemical synapses)
3. Specific connection patterns
4. Connections can be modified by experience *** (very quickly to form rapid
changes, or long term to produce long term changes in behaviour)
^^ Learning facts- synapses changing in brain
LEARNING AND MEMORY:
-Learning is a major vehicle for behavioural adaptation
Studies of learning-important for both normal and abnormal behaviours
-How does drug addiction come about? These addictions are a learned
behaviour
Learning: is the process of acquiring information
Memory: storage and retrieval of information over time
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