Chapter 47 Flashcards
What does the spinal cord do?
Mediate simple reflexes, coordinates movement involving more than one muscle, receives information from descending tracts (pyramidal tract) from higher centers (cortex), sends information (touch/pain) to higher centers in ascending tracts (medial lemniscus) to brain stem, cerebellum, and cortex
What are the different sections of the brain?
Thalamus, Hypothalamus, Pituitary, Brainstem- midbrain, pons, medulla, Spinal Cord, Cerebullum
What is the medial lemniscus?
Large bundle of heavily my myelinated axons that desiccate in the brainstem specifically the medulla
What is a syrinx?
A huge cavity in the spinal cord extending all the way up to the brain.
What is the autonomic nervous system?
Comprises the output pathways of the CNS the control involuntary functions such as heart rate sweating and digestive activities. control of diverse organs and tissues is crucial to homeostasis. Has two divisions- sympathetic and parasympathetic
What is the sympathetic division of the ANS?
Produce the fight-flight response increasing heart rate blood pressure and cardiac output and preparing the body for emergencies.
Preganalinoic fibers are cholinergic and terminate on sympathetic ganglia adjacent to the spinal cord and other nearby ganglia
Postganglionic fibers terminate on organs and are mostly noradenergic (use norepinephrine)
What is a cholinergic?
A neuron that uses acetylcholine neurotransmitter
What is the difference between preganalinoic and postganglionic?
Preganglionic- The second neuron in the pathway with which they synapse resides in a collection of neurons outside the CNS called ganglion, not first
Postganglionic- The second one is called the postganglionic neuron because it’s axon extends out from the ganglion
What is the Parasympathetic division of the ANS?
Slows the heart and lowers blood pressure it’s actions have been characterized as rest and digest
Ganglia tend to be located closer to the target organs, preganalinoic again cholinergic
Fibers terminating on organs are mostly cholinergic (use acetylcholine) or peptidergic (use neurpeptides)
What are the parts of the brain stem?
1) Medulla
2) Pons
3) Midbrain
What are the parts of the Medulla?
Inferior olivary nucleus: receiver inputs from the brain and spinal cord, send outputs to cerebellum (climbing fibers)
Pyramid: Fibers of the pyramidal tract from cortex to spinal cord
Medial lemniscus: Principal ascending pathway from spinal cord for touch and pain
What is the Pons and what does it do?
Located directly below the cerebellum
Contains many descending and ascending tracts to cerebellum from spinal cord and to the spinal cord from the cerebellum
Contains pontine nuclei and pontine tracts that assist in and coordinate massive flow of information from cortex to mossy fibers of cerebellum (control movement)
What are the parts of the midbrain?
Superior colliculus: processes visual and auditory information for control of Eye movements
Periaqueductal gray: Control of pain, stimulation causes inhibition of pain so great that major surgery can be performed without an anesthetic, stimulation can also reduce intractable pain in patients
Substantia nigra: Control of movement, many neurons of this nucleus contain dopamine which they use as a synaptic transmitter, malfunction causes Parkinson’s disease
Cerebral peduncle: contains major descending tracts from cerebellum to spinal cord, control of movement
What does the reticular formation do?
Major role is to control levels of arousal and attention
Ascending projections are very widespread and reach many areas of the brain including cortex
Sustained output from the reticular formation is essential for the maintenance of consciousness, damage to these fibers can produce a prolonged coma
Which parts of the brain do the pathways of reticular formation go?
Cerebral hemisphere, Thalamus, Hypothalamus, Pons, Medualla, Spinal Cord, Midbrain, Cerebellum
What are the inputs of the cerebellum?
Inputs for mossy fibers come directly from spinal cord, the vestibular system, and cortex through pontine nuclei in pons
Mossy fibers synapse onto Granule cells that form from parallel fibers
Parallel fibers synapse onto Purkinje cell dendrites
Inputs from climbing fibers from inferior olivary nucleus in Medulla, these synapse directly onto Purkinje dendrites
What are the outputs of the cerebellum?
Entire output of cerebellum provided by axons of Purkinje cells
Some axons go to the vestibular nuclei and from there directly to spinal cord
Most axons and in three clusters of cells called deep Cerebellular nuclei, axons of the cells form the cerebral peduncle in the midbrain and project too many parts of the brain that are involved in the control of movement
What does the cerebellum do?
Plans movements together with cortex, particularly those that improve with practice
Adjust movements as they are made
Control of posture
Control of eye movements
Motor learning, particularly skilled movements and agility
Cognitive functions (still poorly understood)
What is the basal ganglia?
The principal are the caudate nucleus, putamen, and globus pallidus.
Closely linked in function to the substantia nigra in the midbrain
All function by modulating the flow of information to and from the cortex
Particularly important for the control of movement
What are some diseases associated with basal ganglia?
Degeneration occurs during aging
Huntington disease: hereditary degeneration producing involuntary movements and loss of cognition
Parkinson’s disease: caused by degeneration in basal ganglia, causes tremor and lack of motor control
What is the thalamus?
Sensory input from every major sensory system comes into thalamus
Output from thalamus is to sensory areas of cortex
These areas of the cortex also send strong inputs back into thalamus
This cortical input together with input from the reticular formation act as a gate to regulate the sensory input, so that some sensory input is allowed to enter cortex but other input is kept out
What is the amygdala in the limbic system?
Receives sensory input from all the major senses, especially smell
Outputs project to many parts of brain including basal ganglia and cortex
Stimulation of amygdala produces immediate increase in attentiveness, followed by strong emotion, especially fear.
Destruction of amygdala in animal produces decrease in aggression: animal becomes tame
What is the hippocampus in the limbic system?
Hippocampus and nearby cortical areas are critically important in short term memory, especially the learning of facts (as opposed to the acquiring of skills)
Destruction/removal of hippocampus leaves patients unable to form new memories of facts or events, early memory are largely intact- so are learned skills (piano, tennis)
What is the limbic system?
Structures deep within the cerebral hemispheres and surrounding the hypothalamus control aspects of motivation, drives, emotions, and memory.
Includes the Olfactory bulbs, Hypothalamus, Pituitary, Amygdala, Hippocampus
