Behavior Flashcards
(27 cards)
Central nervous system components
Brain and spinal cord
Peripheral nervous system divisions
Somatic and autonomic. Autonomic further broken down into sympathetic and parasympathetic
Describe a reflex arc
Sensory receptors detect pain > transmit signal up spinal cord through interneurons > interneurons send signals to muscles > muscles respond to reflex. By the time the brain receives the sensory info, the muscles have already responded
Lower motor neurons
- Efferent neurons of PNS; control skeletal muscle
- Efferent neurons in contact with other end of motor unit form neuromuscular junction
- Abnormalities cause weakness
Neuromuscular junction
Interface between lower motor neuron (PNS) and muscle
Lower motor neuron signs (LMN signs)
- Atrophy of skeletal muscle
- Fasciculations (involuntary twitches)
- Hypotonia (decrease in muscle tone; how much muscle is contracted when a person is relaxed)
- Hyporeflexia (decreased muscle stretch reflex)
Fasciculations (definition and cause)
- Involuntary twitches of skeletal muscle
- Caused by abnormalities in lower motor neurons (LMN sign)
Hypotonia (definition and cause)
- Decrease in muscle tone; how much muscle is contracted when a person is relaxed
- Caused by abnormalities in lower motor neurons (LMN sign)
Hyporeflexia (definition and cause)
- Decreased muscle stretch reflex
- Caused by abnormalities in lower motor neurons (LMN sign)
5 main types of somatosensation
- Position
- Vibration
- Touch
- Pain
- Temperature
Mechanoreceptors (types of sensation and key characteristics)
- Position, vibration, and touch
- Found at varying depths: ones in muscle for position, ones in skin for vibration + touch
- Large diameter axons; thick myelin sheath; fast signal transduction
Nociceptors (types of sensation and key characteristics)
- Pain
- Thin myelin sheath; slow signal transduction
- End in uncovered terminals, don’t have big structures like mechanoreceptors
Thermoreceptors (types of sensation and key characteristics)
- Temperature
- Thin myelin sheath; slow signal transduction
- End in uncovered terminals, don’t have big structures like mechanoreceptors
Muscle stretch reflex
- Causes a muscle to contract after it is stretched
- Hammer hits tendon below kneecap, which hooks onto the lower leg bone on one end, and a large group of upper muscles (muscle spindles) on the other
- Afferent somatosensory neurons in muscle spindles form excitatory synapse in spinal cord with another neuron in the spinal cord, which sends axon out to same muscle that was stretched, and excites skeletal muscle cells to contract
- Muscles on underside of leg are inhibited when the topside of leg is excited. Necessary for reflex to occur
Gray matter
- Contains most of the neuron somas
- Spinal cord: gray inside, white outside
- Brain: white inside, gray outside
White matter
- Contains myelinated axons
- Spinal cord: gray inside, white outside
- Brain: white inside, gray outside
Areas controlled by lower motor neurons
- Muscles of limbs and trunk
- LMNs that pass through cranial nerves control muscles of head and neck
Upper motor neurons (cell location, synapse location)
- Found in cerebral cortex
- Synapse on LMNs in brainstem or spinal cord
UMNs: corticospinal tract
UMN white matter pathway: cerebral cortex > down brainstem > spinal cord > axons cross and travel down other side > lower motor neurons
UMNs: corticobulbar tract
UMN white matter pathway: [Need to look up]
Upper motor signs
- Hyperreflexia
- Clonus
- Hypertonia
- Extensor plantar response
Hyperreflexia
- Increase in muscle stretch reflexes
- Muscle spindle receptors become hypersensitive
Clonus
- Rhythmic contractions of antagonist muscle
- Caused by hyperflexia (doctor pulls on foot > activates muscle stretch reflex > triggers antagonist muscles
Hypertonia
Increased tone of skeletal muscles
