exam deck 5 Flashcards
Why can’t simple reflexes alone account for complex movements?
Complex movements require multiple layers of control involving coordinated input from the spinal cord, brainstem, basal ganglia, cerebellum, and cortex.
What types of movements are managed by this complex system?
Reflexive, rhythmic, and voluntary movements
What is the role of central pattern generators (CPGs) in movement?
CPGs are neural circuits that generate rhythmic movement patterns, such as locomotion, independently of sensory input.
Which types of neurons are involved in CPGs, and how are they organized?
CPGs typically include flexor and extensor motor neuron circuits that alternate in activation, often influenced by descending pathways from the brain.
Describe the general pathway of voluntary movement control.
Premotor Cortex: Plans the movement.
Primary Motor Cortex: Selects the motor command.
Basal Ganglia: Refines and organizes the command.
Motor Cortex: Sends the refined command to the body via the corticospinal tract.
Cerebellum: Monitors movement, receiving feedback from the periphery to correct errors in real time.
Spinal Cord and Brainstem Reflexes: Provide support and rapid adjustments during movement.
Which brain areas are involved in coordinating complex movements?
The spinal cord, brainstem, basal ganglia, cerebellum, premotor cortex, and primary motor cortex.
How does the cerebellum contribute during movement?
It continuously adjusts movement by correcting errors based on feedback from sensory inputs.
What are the two main branches of the ANS?
The sympathetic and parasympathetic branches.
How do sympathetic and parasympathetic efferents differ?
They differ in spinal outflow location, ganglia placement, neurotransmitters, and functions.
What neurotransmitter is released by all preganglionic fibers in both sympathetic and parasympathetic systems?
Acetylcholine (ACh), which acts on nicotinic cholinergic receptors.
What neurotransmitter is released by parasympathetic postganglionic fibers, and what receptor does it act on?
Acetylcholine (ACh) acts on muscarinic cholinergic receptors.
What neurotransmitter is released by sympathetic postganglionic fibers, and what receptors does it target?
Noradrenaline (NA), which acts on α and β adrenergic receptors.
What is unique about the sympathetic innervation of the adrenal medulla?
Sympathetic postganglionic cells of the adrenal medulla release adrenaline (~80%) and noradrenaline (~20%) directly into the bloodstream.
What are sympathetic cholinergic fibers, and what do they innervate?
They are sympathetic fibers that release ACh instead of noradrenaline, and they innervate sweat glands.
What are non-adrenergic, non-cholinergic (NANC) transmitters?
NANC transmitters (e.g., peptides) are released by some postganglionic fibers, often alongside conventional neurotransmitters.
Match each spinal region with its function in the ANS.
Cranial and Sacral (Parasympathetic): Outflow for parasympathetic fibers.
Thoracic and Lumbar (Sympathetic): Outflow for sympathetic fibers.
How do somatic and autonomic efferents differ?
Somatic efferents target skeletal muscles, whereas autonomic efferents target smooth muscle, cardiac muscle, and glands with distinct axonal pathways and synaptic mechanisms.
How does sympathetic stimulation affect blood vessels?
Activates α₁ receptors on vessel smooth muscle → contraction → decreased blood flow.
Activates β₂ receptors on vessel smooth muscle → relaxation → increased blood flow.
What is the parasympathetic effect on blood vessels?
Generally, there is no parasympathetic effect on blood vessels.
How does sympathetic stimulation affect salivary glands?
Activates β receptors to stimulate a thick, enzyme-rich secretion.
How does parasympathetic stimulation affect salivary glands?
Activates muscarinic receptors to stimulate a profuse, watery secretion.
How does sympathetic stimulation affect the bladder?
Activates β₂ receptors on bladder wall smooth muscle → relaxation → reduced pressure.
Activates α₁ receptors on sphincter smooth muscle → contraction → stops urination.
How does parasympathetic stimulation affect the bladder?
Activates muscarinic receptors on bladder wall → contraction → increased pressure.
Activates muscarinic receptors on the sphincter → relaxation → allows urination.
What is the effect of sympathetic innervation on the male reproductive tract?
Activates α₁ receptors on the urethra → smooth muscle contraction → causes ejaculation.
What is the effect of parasympathetic innervation on the male reproductive tract?
Activates muscarinic receptors on corpus cavernosum → smooth muscle relaxation → causes erection.
How are autonomic reflexes controlled?
Reflexes are integrated in the brain (hypothalamus, thalamus, brainstem) and can be simple spinal reflexes (e.g., urination in infants) or involve higher control (e.g., learned reflexes).
Describe the baroreceptor reflex.
Baroreceptors detect blood pressure changes, and the brain coordinates sympathetic and parasympathetic responses to adjust heart rate, contraction strength, and blood vessel constriction.
What is the general principle of the fight-or-flight vs. rest-and-digest response?
The sympathetic system prepares the body for “fight-or-flight,” while the parasympathetic system promotes “rest-and-digest” functions.
How does the ANS control organs with single vs. dual innervation?
Tissues with dual innervation usually have antagonistic or complementary effects. Tissues with single innervation (often sympathetic) are controlled by adjusting “tone.”
