Nervous System Flashcards
What is the enteric nervous system and how does it function?
It is the network of neurons buried in the lining of the gastrointestinal tract that controls the function of the digestive system.
The ENS can operate independently of the brain and spinal cord, and communicates with the CNS through the parasympathetic and sympathetic nervous systems. The parasympathetic nervous system stimulates digestive activies, while the sympathetic nervous system inhibits them.
What is the differences between the efferent and afferent division of the PNS, and what type of signal do each carry?
The efferent division delivers motor messages from the CNS to muscles or glands (called effectors), while the afferent division of the PNS brings sensory information to the CNS.
In what ways does the nervous system worok particularly closely with the endocrine system?
Nerve impulses send information about the condition of the body to the hypothalamus, which regulates the release of hormones from the pituitary, which controls other glands.
All body systems ultimately require direction from the nervous system to function properly and maintain homeostasis. Heart rate, digestion, body temperature, movement, and higher functions such as cognitive ability, memory, emotion, and fine motor skills are under the control of the nervous system.
What is the sensory adaptation and what are the two primary categories of receptors in terms of their rate of sensory adaption?
The change in sensitivity that occurs when receptors are exposed to a prolonged stimulus. Phasic receptors (most tactile and chemoreceptors) quickly adapt to a constant stimulus, meaning that action potentials decrease over time and eventually stop. Tonic receptors (proprioceptors, nociceptors, photoreceptors) adapt slowly, constantly alerting the CNS of the stimulus with action potentials.
What are the divisions of the PNS and what does each of them do?
The autonomic system (ANS) and somatic nervous system (SNS). The SNS controls voluntary movements, such as the contraction of skeletal muscles. The ANS controls involuntary movements, such as the contraction of smooth and cardiac muscles, and glandular secretions. The ANS has two subdivisions that tend to work antagonistically. The sympathetic division activates the “rest and digest” functions.
Physiologically, how does the sympathetic nervous system exert its function?
Preganglionic neurons of the sympathetic nervous system release acetylcholine (ACh), which is the stimulus for the release of norepinephrine from postganglionic neurons. Norepinephrine acts on target tissues, prompting a rapid and unified response.
The heart rate increasesm respiration rate increases, blood flow to the heart and skeletal muscle increases, pupils dilate, and glycogen is broken down.
Physiologically, how does the parasympathetic nervous system exert its function?
Both pre- and postganglionic neurons of the parasympathetic nervous system release acetylcholine. The parasympathetic nervous system stimulates events that are slower-paced, and less essential for immediate survival.
The heart rate and respiration rate decrease, blood flow is directed to digestive organs, peristalsis is promoted, pupils constrict, and glycogen is synthesized.
What are mechanoreceptors?
Sensory receptors that respond to changes in pressure or tension
Cutaneous touch receptors such as Meissner’s corpuscles, Markel’s disks, Pacinian corpuscles, and Ruffini endings are all mechanoreceptors, as are the muscle spindles that detect stretching of skeletal muscle and the receptors of the inner ear that detect vibrations.
What do chemoreceptors and nociceptors do?
Chemoreceptors such as olfactory and taste receptors detect the presence of chemicals. Nociceptors detect pain.
What are the four main lobes of the brain and their primary respective functions?
Frontal lobe: short term and working memory and information processing as well as decision- making, planning, and judgment.
Parietal love: toward top of head, sensory input as well as spatial positioning of the body
Occipital lobe: back of the head just above the brain stem; visual input, processing, and output; specifically nerves from the eyes enter directly into this lobe
Temporal lobes: left and right sides of the brain; all auditory input, processing, and output.
What are the parts of the brain stem and their respective functions?
The brain stem (midbrain, pons, medulla oblongata) is an important part of respiratory, digestive, and circulatory functions.
Midbrain: vision and hearing functions
Pons: communicates between cerebrum and medulla
Medulla: connects the spinal cord to the brain; it has an important role with the ANS in the circulatory and respiratory system
What are the functions of the meninges and the basic characteristics of each?
They line the cavity, surround the brain and the spinal cord, and contain cerebrospinal fluid in the subarachnoid space
The vascularized pia mater is adhered to the surface of the brain and the spinal cord. The arachnoid mater contains connective tissue but not nerves or blood vessels. The enervated, vascularized dura mater lies next to the bones and folds inward, separating the brain into different compartments.
What are the names and functions of each of the 12 pairs of cranial nerves?
Olfactory: smell
Optic: sight
Oculomotor: moves eye, adjusts the pupil and lens
Trochlear: moves eye
Trigeminal: chewing, face sensation
Abducens: moves eye
Facial: facial expression and anterior two-thirds of the tongue
Vestibulocochlear: sound
Glossopharyngeal: swallowing, saliva, and taste
Vagus: PNS control
Accessory: swallowing and movement of the head and neck
Hypoglossal: speech and swallowing, tongue muscles
What are the two layers of the spinal cord?
It is made of an exterior layer of white matter that surrounds an interior core of grey matter.
The white matter consists of glial cells and myelinated bundles of axons that form tracts to and from the brain. There are no cell bodies or dendrites in white matter. Grey matter consists mostly of interneurons, but some motor neurons and glial cells. (The axons are mostly unmyelinated, giving the tissue its grey appearance.)
How do afferent and efferent fibers enter/exit the spinal cord?
Afferent fibers enter into the posterior/dorsal aspect of the spinal cord (a region called the posterior grey horn) through the anterior root, while efferent fibers exit on the anterior/ventral aspect (the anterior grey horn) through the posterior root.
The cell bodies of afferent neurons reside in dorsal root ganglia, just outside the spinal cord.
What is a reflex arc?
A neural pathway that triggers a reflex action
It begins with a receptor – the site or organ that receives the stimulus. A sensory neuron carries the impulse along the afferent pathway to the integration center within the CNS. Interneurons process the information and pass the impulse to a motor neuron. The impulse travels along the efferent pathway to the effector – the responding muscle or gland.
What are positive and negative feedback loops, respectively?
Positive feedback loops are less common and sometimes harmful because they enhance the stimuli rather than inhibit them. Negative feedback loops inhibit the stimulus or the deviation from homeostasis to bring the body back to the set point.
What are the structural components of a neuron?
Cell body (soma): contains a nucleus with a prominent nucleolus, organelles, no centrioles
Axon: smooth, cable-like nerve fiber that is specialized to conduct electrical impulses away from the soma. Most neurons have one long axon, but the axons length can vary, and some neurons have no axon at all
Dendrites: relatively short, branched extensions of the cell body that receive neurotransmitters from the other neurons.
What is myelin and what does it do?
A lipid-based coating that insulates the axon of many neurons much like the coating on electrical wire. It also increases the rate at which an impulse can travel.
There are intermittent gaps in the sheath called nodes of Ranvier that allow the impulse to jump quickly from one node to the next
What types of cells myelinate neurons in the PNS and CNS, respectively?
Neurons of the peripheral nervous system are myelinated by Schwann cells. Oligodendrocytes sheath the neurons of the central nervous system.
Unlike Schwann cells, a single oligodendrocyte can myelinate dozens of axons by extending its membrane in multiple directions and wrapping around the axons. White matter of the CNS is made mostly of myelinated axons, while the axons associated with grey matter are unmyelinated.
What are neuroglia?
Glial cells support and protect neurons within the central and peripheral nervous system.
Despite their inability to conduct impulses, there are many more glial cells than neurons within nervous tissue.
What are the types and the respective functions of PNS and CNS glial cells, respectively?
CNS: astrocytes (anchor neurons, exchange between capillaries and neurons, uptake excess ions and neurotransmitters), microglia (immune defense, digest dead debris), oligodendrocytes (produce myelin sheaths), ependyma (circulate CSF)
PNS: satellite cells (surround and cushion PNS neurons), Schwann cells (produce myelin sheaths)
What happens when an action potential reaches the axon terminal?
Voltage-gated calcium channels open in response to the depolarization of the membrane. Calcium ions enter, triggering the release of neurotransmitters by exocytosis. The neurotransmitters diffuse across the synaptic cleft, binding to receptors in the target cell and eliciting either an excitatory or an inhibitory response.
The neurotransmitters are then recycles back to the presynaptic cell, degraded by enzymes, or diffused away from the synaptic cleft to prevent overstimulation.
The ___ integrates sensory information, and the ___ sends information to and from the ___, allowing it to communicate with the rest of the body.
CNS; PNS; CNS
The ___ controls voluntary movements, such as the contraction of skeletal muscles.
SNS
The ___ controls involuntary movements, such as the contraction of smooth and cardiac muscles, and glandular secretions.
ANS
___ respond to changes in pressure or tension.
Mechanoreceptors
____ are taste receptors that detect the presence of chemicals.
Chemoreceptors
____ respond to light.
Photoreceptors
____ sense both absolute temperature and changes in temperature.
Thermoreceptors
