Lecture 2 - CNS Structure and Function Flashcards
Acetylcholine (What is it secreted by?)
Pyramidal cells of cerebral cortex, some neurons in basal nuclei, alpha motor neurons, preganglionic neurons of ANS, postganglionic neurons of the parasympathetic, some postganglionic neurons of sympathetic
Usually excitatory
Norepinephrine (What is it secreted by?)
Many neurons located in the brain stem and hypothalamus, some neurons located in the pons (locus ceruleus), and most postganglionic neurons of the sympathetic
Can be either excitatory or inhibitory
Dopamine (What is it secreted by?)
Most neurons originating in the substantia nigra
Usually inhibitory
Norepinephrine (What is it targeted by?)
Amphetamines, cocaine, cymbalta, propranolol
Acetylcholine (What is it targeted by?)
Nicotine, chantix, sarin, aricept (Alzheimer’s), botox, tensolin (myasthenia gravis), biperiden (Parkinson’s)
Dopamine (What is it targeted by?)
Amphetamines, cocaine, levadopa (Parkinson’s), haldol (antipsychotic)
Glycine (What is it secreted by?)
Synapses in the spinal cord
- Always inhibitory*
- Not targeted by drugs*
GABA (What is it secreted by?)
Many areas in the spinal cord and cerebral cortex
Always inhibitory
Glutamate (What is it secreted by?)
Many sensory pathways entering the CNS and many areas of cerebral cortex
Always excitatory
GABA (What is it targeted by?)
Alcohol, barbituates, valium, baclofen
Glutamate (What is it targeted by?)
Ketamine (anesthetic), namenda (Alzheimer’s), robitussin
General characteristics of dendrites
May extend out a large distance and receive signals from a large spatial area, generally cannot transmit action potentials (use electronic conduction), long, have thin membranes partially permeable to K+ and Cl-
Decremental Induction
Gradual loss of electric potential in dendrites as the depolarization spreads from the site of initiation because of leakage
Electronic Conduction
Direct spread of electrical current by ion conduction in the dendritic fluids without generating an action potential
Synaptic Delay
Time it takes to transmit a signal from a presynaptic neuron to a postsynaptic neuron; depends on several factors (Slide 19); minimal time is 0.5msec
Vertebral Arteries
First branches of the subclavian arteries, ascend through the transverse foramina of C1-6, pass through the foramen magnum, and unite at caudal border of pons to form basilar artery; basilar artery gives off cerebellar arteries and then divides into two posterior cerebral arteries
Internal Carotids (Component of Circle of Willis)
Terminal branches of the common carotids; enter cranial cavity through carotid canal in temporal bone; give off anterior and middle cerebral arteries
Circle of Willis
Pentagonal-shaped circle of arteries on the ventral surface of the brain that unites the 2 vertebral and 2 internal arteries; important anastomosis between these 2 pairs of arteries
Posterior Cerebral Arteries (Component of Circle of Willis)
Terminal branches of the basilar artery
Posterior Communicating Arteries (Component of Circle of Willis)
Connect the posterior cerebral arteries to the internal carotids
Anterior Cerebral Arteries (Component of Circle of Willis)
Branches off the internal carotids
Anterior Communicating Artery (unpaired) (Component of Circle of Willis)
Connects the 2 anterior cerebral arteries
Components of Telencephalon
Cerebral hemispheres, olfactory bulb, basal nuclei (ganglia), corpus striatum (nuclei in cerebrum), caudate nucleus, lentiform nucleus
Characteristics of Cerebral Hemispheres
Make up 80% of brain mass, have gyri/sulci, left and right are called “falx cerebri”, superior to the cerebellum is called “tentorium cerebelli”, have 5 (maybe 6?) lobes
Occipital Lobe
Integrates eye focusing movements, correlates visual images with visual memory, involved in conscious perception of vision, separated from parietal lobe via Parietooccipital Sulcus
Parietal Lobe
Somatesthetic interpretation (postcentral gyrus), understanding speech at auditory association complex and Wernicke’s area, formulating words to express thoughts and emotions
Central Sulcus
Landmark that separates the motor cortex from the sensory cortex
Frontal Lobe
Voluntary motor control (precentral gyrus), motivation, aggression, mood, personality, cognitive processes, verbal communication (Broca’s area)
Temporal Lobe
Receives/interprets olfactory and auditory sensations, responsible for storage of memory related to auditory and visual experiences
Insula Lobe
Not observed from the surface; involved with memory, psychic cortex; highest levels of brain function (abstract thought and judgement)
Corpus Striatum Components
Caudate nucleus and lentiform nucleus
Caudate Nucleus
Large subconscious movements of skeletal muscles
Lentiform Nucleus
Has a putament (in control of large subconscious movements of skeletal muscles) and globus pallidus (regulates muscle tone)
Components of Diencephalon
Epithalamus, pineal body, thalamus
Epithalamus
Has habenular nuclei; thought to be involved in emotional and visceral responses to odors, projects to septal nuclei (in thalamus) via stria medullaris thalami, and projects to interpeduncular nucleus via habenulointerpeduncular tract
Pineal Body
Secretes melatonin (regulates circadian rhythms); activity is modulated by light-dark cycle via sympathetic inputs activated by hypothalamic suprachiasmatic nucleus; calcification accrues with maturity; lesions associated with precocious puberty
Thalamus
Makes up 80% of diencephalon, separated by hypothalamus via hypothalamic sulcus; has optic recess, infundibular recess, and pineal recess as landmarks; has habenular commissure ABOVE the pineal recess and posterior commissure BELOW the pineal recess
Functions of the Thalamus
Relays all sensory information except smell to the cerebral cortex, provides crude awareness, initial autonomic response of the body to intense pain (physiologic shock), interpretation center for crude pain, temperature, light touch, pressure, plays a role in arousal and alerting, and plays a role in complex reflex movements
Thalamic Sensory Relay Nuclei
Medial geniculate body (auditory; projects to primary auditory cortex in temporal lobe), lateral geniculate body (visual; projects to primary visual cortex in occipital lobe), and ventral posterior nuclei (general sensations and taste)
Thalamic motor Relay Nuclei
Ventral lateral (voluntary motor), ventral anterior (voluntary motor and arousal), subthalamic
Thalamic Reticular Nucleus
Modifies neuronal activity in the thalamus; may be involved in regulating sleep-wakefulness cycle and levels of awareness
Thalamic Anterior Nuclei
Concerned with certain emotions and memory; receives input from hippocampus and mammillary bodies (mammillo)
Functions of Reticular Formation
Modulates sensation of pain, modulates certain postural reflexes and muscle tone, helps control breathing and heartbeat, regulates level of brain arousal and consciousness, made up of diffuse aggregations of cells
Magnocellular Zone
Large cells restricted to medial 2/3 of reticular formation
Parvocellular Zone
Small cells found in lateral regions of reticular formation
Raphe Nuclei
Lie along midline of medulla and midbrain; important in maintaining wakefulness; damage may result in permanent coma
Monoaminergic Pathways of RAS
Uses serotonin, norepinephrine (noradrenaline), and dopamine
Serotonergic Pathways of RAS
Originate in raphe nuclei; extensive continuous collection of cell groups throughout the brainstem; one part terminates in substantia gelatinosa and is implicated in pain mechanisms; other part projects to limbic structures and may be associated with changes in mood and behavior; may be part of sleep-inducing mechanism
Inhibition of serotonin synthesis or destruction of raphe nuclei leads to insomnia, but can be cured by administration of serotonin
Noradrenergic Pathways of RAS
One system arises from lateral reticular formation and innervates the hypothalamus and other limbic structures; best-known group of cells is in the locus ceruleus (heavily pigmented cells) which projects to every major region of the brain and spinal cord; most adrenergic fibers terminate on small blood vessels and capillaries in the brain and may help regulate flow in the brain
Dopaminergic Pathways of RAS
Majority of dopaminergic cells are located in the substantia nigra
