Topic 5: NS - Integration and Control (Brain + Spinal Cord) Flashcards
what is the role of the spinal cord?
-transmit signals to and from the brain via ascending sensory tracts and descending motor tracts
-integrates and executes somatic and autonomic reflexes
what are reflexes?
-rapid automatic responses to stimuli
-stimulus always causes the same motor response
-usually protective
how many neurons are involved in a reflex?
-2 or more
what is a reflex pathway/arc?
-pathway of impulses
-stimulus > receptor > CNS > effector
what are the 3 factors that categorize a reflex?
-the effector
-the side of the body that the sensory and motor neurons are located on
-the number of synapses (and neurons) in the reflex arc
what are the 2 categories of reflexes based on the effector?
-somatic reflex (effector = skeletal muscle)
-visceral (autonomic) reflex (effector = smooth muscle, cardiac muscle, or glands)
what are the 2 categories of reflexes based on the sides of the body that the sensory and motor neurons are located?
-ipsilateral reflex (sensory + motor neurons are on the same side)
-contralateral reflex (sensory + motor neurons are on opposite sides)
what are the 2 categories of reflexes based on the number of synapses/neurons in a reflex arc?
-monosynaptic reflex = 1 synapse between 1 sensory and 1 motor neuron
-polysynaptic reflex = 2 or more synapses between 3 or more neurons
what are 3 examples of types of somatic spinal reflexes?
-stretch reflex
-flexor (withdrawal) reflex
-crossed extensor reflex
what is a stretch reflex?
-automatic muscle contraction in response to sudden or excessive stretching
-helps maintain muscle tone
-stabilizes posture and balance
-prevents injury (protective)
what is an example of a stretch reflex? what are the different parts of this reflex? what is it categorized as?
-knee jerk reflex
-stimulus = tapping the patellar ligament (stretches the quadriceps femoris muscle b/c connected)
-receptor = muscle spindle in the quadriceps
-effector = skeletal muscle (quadriceps contracts (extension))
-ipsilateral
-monosynaptic (quick, do not want the arc to be long)
what is an example of a flexor (withdrawal) reflex? what are the different parts of this reflex? what is it categorized as?
-in the leg
-stimulus = stepping on a nail
-receptor = touch, pressure, pain
-effector = flexor hamstrings contract
-ipsilateral
-polysynaptic
what is a flexor (withdrawal) reflex?
-automatic contraction of flexor muscles that move parts of the body (typically a limb) away from a painful stimulus
what is a crossed extensor reflex?
-automatic contraction of extensor muscles in the opposite limb during a withdrawal reflex
-keeps the body balanced and supported to protect from injurt
what is an example of a crossed extensor reflex? what are the different parts of this reflex? what is it categorized as?
-in the leg
-stimulus = stepping on a nail
-receptor = touch, pressure, pain
-effector = quadriceps femoris in the opposite leg (extensor contracts)
-contralateral
-polysynaptic
what is the purpose of the crossed extensor reflex occurring in conjunction with the flexor (withdrawal) reflex
-keeps you from falling down when the withdrawal reflex occurs in the leg that stepped on the nail
what is the concept of reciprocal inhibition?
-the inhibition of somatic lower motor neurons to antagonist muscles during contraction of an agonist muscle
-ensures smooth and coordinated movements by allowing the agonist muscle (or group of muscles) to contract while the antagonist muscle (or group of muscles) relax
how does reciprocal inhibition work in the stretch reflex?
-quadriceps femoris (agonist) contracts
-hamstrings (antagonists) contraction inhibited
what is an example of an autonomic spinal reflex? what are the different parts of this reflex?
-micturition reflex (urinary bladder)
-stimulus = stretch of the bladder
-receptor = stretch receptors in the bladder wall
-CNS = sacral segment of the spinal cord (PSNS) (does not need to travel to the brain)
-effector = detrusor muscle (wall of the bladder) contracts and the internal urethral sphincter opens (both are smooth muscle)
what is the role of the brain?
-transmits signals to and from the brain via ascending and descending tracts
-integrates and executes somatic and autonomic reflexes
what is the role of the cerebrum?
-interprets sensory information from general and special senses
-initiates and controls skeletal muscle movement (has motor areas and basal nuclei)
-controls higher functions such as memory, intellect, language, and emotional regulation
-relays info between different parts of the brain and/ to/from the spinal cord (has association, commissural, and projection tracts)
what is the role of the brain stem?
-controls life sustaining processes such as breathing and circulation
what would happen to a person if their brain stem was functional but higher centers were damaged?
-person would be physiologically alive but not be aware or have conscious control
what are the 3 parts of the brain stem?
-midbrain
-pons
-medulla oblongata
