Lesson 5 Flashcards
2 main functions of the spinal cord:
- Propagates nerve impulses
- Integrates information
2 main sensory tracts
- Spinothalamic tract
- Posterior column
Spinothalamic tract
- conveys nerve impulses for sensing pain, temperature, itch, tickle, and touch, pressure, vibration
Posterior column
- made up of 2 tracts gracile fasciculus & cuneate fasciculus
- conveys nerve impulses for touch, light pressure, vibration and conscious proprioception
Conscious proprioception
the awareness of the positions and movements of muscles, tendons and joints
2 main motor tracts
- Direct pathways
- Indirect pathways
Direct pathways
- lateral corticospinal tract
- anterior corticospinal tract
- corticobulbar tract
- nerve impulses originate in cerebral cortex
- cause voluntary movements of skeletal muscle
Indirect pathways
- rubrospinal tract
- tectospinal tract
- vestibulospinal tract
- lateral reticulospinal tract
- medial reticulospinal tract
Indirect pathways nerve impulses and functions
- nerve impulses originate in brain stem
- causes automatic movements
- helps coordinate body mvts with visual stimuli
- maintains skeletal muscle tone
- sustained contraction of postural muscles
- major role in equilibrium by regulating muscle tone in response to movements of head
Stimulus
- a change in the internal or external environment
Reflex
- a fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimulus
- can be inborn or learned
*Spinal reflex
- when integration happens in grey matter of SC
Cranial reflex
- when integration happens in brain stem
Somatic reflex
- involves contraction of skeletal muscle
Autonomic reflexes
- not usually consciously perceived
- involve responses of smooth mm, cardiac mm and glands
Reflex Arc
- the reflex arc or reflex circuit is the pathway for nerve impulses that produce a reflex
Reflex arc 5 components
- Sensory receptor
- Sensory neuron
- Integrating center
- Motor neuron
- Effector
monosynaptic reflex arc
- most simple
- a reflex pathway with only 1 synapse in the CNS (so 2 neurons and 1 synapse)
Polysynaptic reflex arc
- when the integrating center consists of at least one interneuron
- involves more than 1 synapse in the CNS (so 3 neurons and 2 synapses)
The stretch reflex
- contraction of a skeletal muscle in response to stretching of that muscle
- monosynaptic reflex arc
- can be elicited by tapping on tendons attached to muscles at elbow, wrist, knee and ankle joints
- stimulates muscle spindles
- muscle spindles are sensory receptors in the mm
- they monitor the change in length of the mm
- the stretch reflex is an ipsilateral reflex
- sensory nerve impulses enter the same side that the motor nerve impulses come out
The stretch reflex
mm tone
-tone of a muscle is also set through muscle spindles
Muscle tone = the small degree of contraction present when a muscle is at rest
Stretch reflex
Reciprocal innervation
- when parts of a neural circuit simultaneously cause contraction of 1 muscle and relaxation of its antagonists
Stretch reflex
mm spindles relay info where?
-branches of the muscle spindle sensory neuron also relays information to the brain so that you know what is happening
The tendon reflex
- relaxation of a muscle when there is too much tension
- prevents tearing of a tendon
- ipsilateral
- polysynaptic
- stimulates Golgi tendon organs (GTO)
Tendon reflex
Protects mm from what?
- this reflex protects the tendon and muscle from damage due to excessive tension
- reciprocal innervation
The flexor (withdrawal) reflex
- when you step on a tack, you will flex or withdraw your leg away from the painful stimulus
- it is a polysynaptic reflex arc
- it is ipsilateral
- this is a protective reflex because it moves the limb away from a possibly damaging stimulus
The flexor (withdrawal) reflex
Type of reflex arc?
-it is an intersegmental reflex arc
-nerve impulses from 1 sensory neuron ascend and descend in the spinal cord, activating interneurons in several segments of the spinal cord
-this way a single sensory neuron can activate several motor neurons
The crossed extensor reflex
- happens with the flexor reflex
- when you step on a tack and withdraw or flex your leg, the other leg needs to extend so you don’t fall over
- this is a contralateral reflex arc
- sensory impulses enter one side of the spinal cord and motor impulses exit on the opposite side
- intersegmental reflex arc
- reciprocal innervation
