Nervous System 3 - Integration & Control (Brain & Spinal Cord) Flashcards
Lec 10
What is the fxn of the brain and spinal cord in maintaining homeostasis?
integration of signals from the afferent pathways, and then the processing of info to coordinate the proper response within the effectors. so the sensory/afferent division inputs info to brain and SC (control centres) and then they integrate info and control effectors through the motor/efferent division which is the output.
What is the fxn of the spinal cord (simple)?
transmit signals to and from the brain via ascending (sensory) and descending (motor) tracts/pathways. integrates and executes somatic and autonomic reflexes. so info doesnt need to go all the way to brain for reflexes to happen.
What are reflexes?
rapid automatic responses to stimuli or multiple stimuli. a stimulus always causes the same motor response, so reflexes do not differ. reflexes are usu protective, so for safety to keep you from falling. involve 2 or more neurons (ie sensory and motor neuron). a reflex pathway or arc is a pathway of impulses, so get stim which is detected by receptor, and transmitted to CNS which then sends a signal to the effectors.
How can reflexes be categorized (list)?
by effector, which sides of the body the sensory and motor neurons are located, and the number of synapses and neurons in a reflex arc.
What are the different kinds of effectors in reflexes?
- somatic reflex - effector is skeletal mm (body) 2. visceral (autonomic) reflex - effector is smooth mm, cardiac mm or glands (organs/viscera).
What are the categories for which sides of the body the sensory and motor neurons are located on for reflexes?
- ipsilateral reflex - sensory and motor neurons are on the same side of the body. 2. contralateral reflex - sensory and motor neurons are on oppo sides of the body (so receptor on one side and effector on other)
What are the categories for number of synapses and neurons in a reflex arc?
- monosynaptic reflex - one synapse btwn one sensory and one motor neuron. 2. polysynaptic reflex - 2 or more synapses btwn 3 or more motor neurons. (so prob an interneuron involved)
What are some examples of a somatic spinal reflex (list)?
stretch reflex, flexor/withdrawal reflex, and crossed extensor reflex.
What is a stretch reflex and an example?
an automatic mm contraction in response to sudden or excessive stretching that helps maintain mm tone, stabilize posture and balance and prevent injury. ex is knee jerk reflex where the extensor mm contracts. stimulus = tapping patellar tendon which stretches the quadriceps femoris mm (causing it to contract). receptor = mm spindle in quad that monitors stretch. effector = skel mm (quads) contracts. reflex is ipsilateral and monosynaptic.
What is a flexor/withdrawal reflex and an example?
automatic contraction of flexor mms that moves a part of the body (usu a limb) away from a painful stimulus. ex is in leg; stimulus = stepping on a nail receptor = touch, pressure, pain effector = skel mm, hamstrings (flexors) contract lifting leg away from stimuli. reflex is ipsilateral and polysynaptic.
What is a crossed extensor reflex and an example?
an automatic contraction of extensor mms in the oppo limb during a withdrawal reflex. keeps body balanced/supported to protect from injury. ex in leg; stimulus = stepping on nail receptor = touch, pressure, pain effector = skel mm, quads femoris in oppo leg (extensor) contracts. reflex is contralateral and polysynaptic. goal is to keep you from falling down when withdrawal reflex occurs in oppo leg stepping on nail.
What is an agonist mm?
the mm working/ contracting.
What is an antagonist mm?
the mm at rest/lengthening.
What is reciprocal inhibition?
the inhibition of somatic lower motor neurons to antagonist mms during contraction of agonist mm. so make the antagonist mm relax. ensures smooth and coordinated mvmt by allowing agonist to contract and antagonist to relax.
What is an example of reciprocal inhibition?
the stretch reflex where the quads femoris (agonist) contracts and the hamstrings (antagonist) contraction is inhibited.
What is an autonomic/visceral spinal reflex and an example?
a reflex within the smooth mm, cardiac mm or glands. ex Micturition reflex in the urinary bladder. stimulus= stretch of the bladder. receptor = stretch receptors in bladder walls. CNS= sacral segment of spinal cord (PSNS) effector= detrusor mm in wall of bladder which contracts and internal urethral sphincter opens.
What is the function of the brain in relation to the pathways (simple)?
integrates and executes somatic and autonomic reflexes and receives info from the sensory pathway and sends info down effector pathway.
What are the parts of the brain relevant to integration and control (that we covered)?
cerebrum. brain stem - midbrain, pons, medulla oblangata. hypothalamus
What is the fxn of the cerebrum?
interprets sensory info from general and special senses. initiates and controls skel mm mvmt (motor areas and basal nuclei). higher fxns like memory, intellect, lang, emotional regulation. relaying info btwn diff parts of the brain and/or to or from the SC (association, commissural, projection tracts)
What is the fxn of the brainstem?
controls life-sustaining processes like breathing and circulation. if the brain stem is fxnl but higher centres are damaged, a person would be physiologically alive but would not be aware or have conscious control.
What is the fxn of the midbrain within the brain stem?
auditory and visual reflexes, so the mvmt of eyes, head and neck in response to visual/auditory stimuli.
What is the fxn of the pons within the brain stem?
works with medulla to reg breathing (pontine respiratory centres).
What are the fxnl regions of the medulla oblongata within the brain stem?
- decussation (crossing) of sensory tracts. ie the left brain controls right skel mms. 2. autonomic vital reflex centres; a. respiratory area - drives breathing rate b. cardiovascular centres - cardiac centre which modifies HR and the vasomotor area which controls bl vessel diameter. 3. other non-vital areas - control swallowing, coughing, sneezing, vomiting, etc.
What is the fxn of the hypothalamus?
- reg ANS (glands, smooth mm, cardiac mm) 2. reg parts of endo syst 3. regs temp 4. reg food and water intake, bodily fluid conc 5. part of limbic syst which is the emotional brain 6. part of reticular activation (RAS), with the reticular formation in the brain stem cortex and thalamus. has an alerting fxn when awake and receives sensory input for awakening so sets sleep/wake cycle. So, the hypothalamus controls all major homeostatic fxns.
