Neuro PPT 2 Flashcards
What serves as the integrative area for cord reflexes?
Cord Grey matter
Where do sensory signals enter the spinal cord?
Sensory roots (Posterior or dorsal roots)
Sensory signals have Two destinations in the spinal cord. What are they?
Local segmental reflexes - this branch terminates in the gray matter for local reflexes
Higher system transmission: this branch sends signals to higher nervous system levels (brain stem, cortex)
What are anterior motor neurons?
Large neurons located in the anterior horns and directly innervate muscles. Transmit impulses quickly.
Three types:
alpha motor neurons
Gamma motor neurons
Renshaw cells
What are interneurons
Found in the gray matter, highly excitable and integral to reflex arcs
Alpha motor neurons give rise to ________ motor nerve fibers
A alpha
What do alpha motor neurons do?
Stimulates multiple skeletal muscle fibers (ie: motor unit)
What do gamma motor neurons innervate?
Intrafusal fibers
Gamma motor neurons are _______ fibers
Small
Gamma motor neurons give rise to ______ motor nerve fibers
A gamma
Stimulation of the intrafusal fibers by gamma motor neurons helps control _______ ________ _______
Basic muscle tone
Where are interneurons located?
Widely distributed throughout the cord gray matter
ie: dorsal horns, intermediate areas, anterior horns
Function of interneurons
Process and relay signals
Extensive Interconnections responsible for spinal integrative functions: diverging, converging, repetitive-discharge
Location of renshaw cells
Anterior horn of the gray matter
Closely associated with anterior motor neurons
Function of renshaw cells
Refines motor control by transmitting INHIBITORY signals from the anterior motor neuron to adjacent motor neurons
Causes lateral inhibition
Function of propriospinal fibers
Form communications between spinal cord segments to coordinate multi-segmental reflexes, allowing coordination of movement between extremities.
Two types of muscle sensory receptors
Muscle spindles and golgi tendon organs
Function of muscle sensory receptors
Provide continuous feedback of sensory information about muscle length and tendon tension
Muscle spindles
State location and function
Location: muscle belly
Function: senses muscle length and rate of change of length
Golgi Tendon Organs
State location and function
Location: tendons
Function: senses tendon tension and rate of change of tension
Feedback from the muscle sensory receptors is sent to which 3 areas?
Spinal cord
Brain stem
Motor areas of cerebral cortex
Muscle spindles consist of …
3-12 intrafusal fibers that taper at the ends to connect to larger extrafusal muscle fibers
T/F: Continuous transmission of nerve signals is
required for function of the cerebral cortex
True
How much time does direct stimulation effects persist for?
Milliseconds or seconds
How much time does neurohormonal systems effects persist for?
Minutes or hours
Location for the reticular excitatory area:
Pons/mesencephalon
Where are facilitatory signals transmitted to?
Spinal cord and cerebral cortex
Location of the reticular inhibitory areas:
Medulla
_________ releasing nerve fibers from locus ceruleus transmit signals
throughout brain
Primarily excitatory effects, possibly involved in dreaming
Norepinephrine
____________ nerve fibers from raphe nuclei (i.e., medulla and pons) transmit
signals to spinal cord, diencephalon, and cerebral cortex
At spinal cord level, it is involved in pain suppression
At diencephalon and cerebral cortex level, it has inhibitory effects,
possibly involved in regulation of sleep
Serotonin
_________ nerve fibers from substantia nigra transmit signals to caudate
nucleus, putamen, hypothalamus, and limbic system
Primarily inhibitory effects, possibly some excitatory effects
Dopamine
__________ nerve fibers from gigantocellular neurons of reticular excitatory area
transmit signals to spinal cord and higher brain levels
Primarily excitatory effects, possibly involved in wakefulness
Acetylcholine (Cholinergic)
What system:
Controls emotional behavior and motivational drive
Reward/Punishment (i.e., pleasant/unpleasant)
Vegetative functions (e.g., control of body temperature,
control of osmolality of body fluids, hunger, thirst)
Limbic System
Anatomy of the Limbic System:
SUBCORTICAL STRUCTURES
Hypothalamus- central physiologic function
Septum area, paraolfactory area, anterior nucleus of
thalamus, portions of basal ganglia, hippocampus,
amygdala
LIMBIC CORTEX
Orbitofrontal cortex, subcallosal gyrus,
cingulate gyrus, parahippocampal gyrus
Medial forebrain bundle extends from orbitofrontal
cortex through hypothalamus to brain stem reticular
formation
Two-way communication exists between hypothalamus and all levels of limbic system:
- Transmits signals to brain stem then to
peripheral nerves of ANS - Transmits signals to anterior thalamus and other
structures of limbic system - Transmits signals to hypothalamic infundibulum to
control secretion from pituitary gland
What are the seven functions of the hypothalamus?
- cardiovascular regulation
- body temperature regulation
- body water regulation 4. regulation of uterine contraction and milk
ejection - gastrointestinal regulation
- circadian rhythm
- pituitary
gland regulation
Sensory experiences cause activation of
___________, which sends signals to
anterior thalamus, hypothalamus, and other
structures of limbic system
Hippocampus
What are the two functions of the hippocampus?
- Formation of memories
- Consolidation of memories
Anatomy of the amygdala:
Group of nuclei situated inferiorly to medial
anterior pole of temporal lobe
Two-way communication with cerebral
cortex, hippocampus, septum, thalamus,
and, in particular, the hypothalamus
What are the functions of the amygdala?
(Stimulation causes same effects as direct stimulation of the hypothalamus
- tonic and clonic movements
- circling
movements - movements associated
with olfaction and eating (licking,
chewing, swallowing) - Reward/Punishment patterns
- Activities of reproductive organs