EXAM 2 BRAIN AND CRANIAL NERVES Flashcards
What are meninges?
Three membranes surrounding brain and spinal cord
What is the function of the meninges?
Protect the brain and provide structural framework for its arteries and veins
What are the three meninges from most superficial to most deep?
Dura mater
Arachnoid mater
Pia mater
Dura mater
- presses closely against cranial bones
- no epidural space (unlike spinal cord)
- not directly attach to bone except around foramen magnum, sella turcica, crista Gallo, and sutures of the skull
Folds of dura mater extend inward, separating some brain regions into the folllowing
- falx cerebri: separates the 2 cerebral hemispheres
- tentorium cerebelli: separates cerebrum from cerebellum
- falx cerebelli: separates right left halves of cerebellum
Arachnoid mater
- transparent membrane over brain surface
- subarachnoid space separates it from pia mater below
Pia mater
- very thin membrane, not usually visible without microscope
- follows all contours of brain
- follows arteries as they penetrate into cerebrum
What is the brain protected by?
At the blood capillaries, the brain is protected by the blood-brain barrier
What makes up the blood-brain barrier?
Consists of tight junctions between endothelial cells that form the capillary walls
What is the process of the blood-brain barrier?
- During development, astrocytes reach out no contact capillaries with their perivascular feet
- this induces the endothelial cells to form tight junctions that completely seal off gaps between them
Anything leaving the blood must pass through what?
Anything leaving the blood must pass through the cells and not the gaps between them
What can endothelial cells be unlike simple gaps?
Endothelial cells can be selective unlike simple gaps
What are the 4 lobes that make up the brain?
- frontal lobe
- parietal lobe
- occipital lobe
- temporal lobe
What is the function of the frontal lobe?
Voluntary motor functions, motivation, foresight, planning, memory, mood, emotion, social judgement, and aggression
What are the functions of the parietal lobe?
Integrates general senses, taste, and some visual info
What is the function of the occipital lobe?
Primary visual center of brain
What is the function of the temporal lobe?
Functions in hearing, smell, learning, memory, and some aspects of vision and emotion
What is the function of insula (hidden by other regions)?
Helps in understanding spoken language, taste and integrating info from visceral receptors
What is the primary sensory cortex?
Sites where sensory input is first received and one becomes conscious of the stimulus
What is the primary visual cortex?
Bordered by visual association areas: make cognitive sense of visual stimuli
What are multimodal association areas?
Receive input from multiple senses and integrate this into an overall perception of our surroundings
What are pyramidal cells of the precentral gyrus called?
Upper motor neurons
Things about upper motor neurons
- their fibers project caudally
- about 10 million fibers ending in nuclei of the brainstem
- about 1 million forming the corticospinal tracts
- most fibers decussate in lower medulla oblongata
- form lateral corticospinal tracts on each side of the spinal cord
In brainstem or spinal cord the fibers from upper motor neurons synapse with what?
Lower motor neurons whose axons innervate skeletal muscles
Where is Wernicke area located?
-posterior to lateral sulcus usually in left hemisphere
Where is Broca area located?
Inferior prefrontal cortex usually in left hemisphere
Broca area generated motor programs for the muscles of
- larynx
- tongue
- cheeks
- lips for speaking and for hands when signing
Function of Broca area
Transmits program to primary motor cortex for commands to the lower motor neurons that supply relevant muscles
Function of Wernicke area
- permits recognition of spoken and written language
- when we intend to speak, Wernicke area formulated phrases and transmits plan of speech to Broca area
Where is affective language area?
Usually in right hemisphere
What do lesions produce in Broca area?
Aprosody (flat emotionless speech)
What are the three parts of the diencephalon?
- thalamus
- hypothalamus
- epithalamus
Thalamus of the diencephalon
- ovoid mass on each side of the brain
- perched at the superior end of the brainstem beneath the cerebral hemispheres
- constitutes about 4/5 of the diencephalon
- composed of at least 23 nuclei within 5 major functional groups
What function does thalamus have in diencephalon?
Plays key role in motor control
-relays signals from cerebellum to cerebrum
-provides feedback loops between the cerebral cortex and the basal nuclei
Involved in memory and emotion
-limbic system includes some of the anterior thalamus nuclei
Hypothalamus is major control center of what systems?
Autonomic nervous system and endocrine system
What are the functions of hypothalamic nuclei?
Hormone secretion
-controls anterior pituitary, thereby regulating growth, metabolism, reproduction, and stress responses
Autonomic effects
-major integrating center for autonomic nervous system
-influences heart rate, blood pressure, gastrointestinal secretions, motility, etc
What are the hypothalamic functions?
Thermoregulation
Food and water intake
-regulates hunger and satiety; responds to hormones influencing hunger, energy expenditure, and long-term control of body mass
-thirst center monitors osmolarity of blood and can stimulate production of anti diuretic hormone
Sleep and circadian rhythms
-suprachiasmatic nucleus sits above optic chiasm
Memory
-mammillary nuclei receive signals from hippocampus
Emotional behavior and sexual response
-anger, aggression, fear, pleasure, contentment, sexual drive
What is the epithalamus of the diencephalon composed of?
- pineal gland: endocrine gland
- habenula: relay from the limbic system to the midbrain
- thin roof over the third ventricle
Cranial Nerves
Brain must communicate with rest of body
- 12 pairs of cranial nerves arise from the base of the brain
- exit the cranium through foramina
- lead to muscles and sense organs located mainly in the head and neck
Where do most motor fibers of the cranial nerves begin?
In nuclei of brainstem and lead to glands and muscles
Where do sensory fibers begin and lead to?
Sensory fibers begin in receptors located mainly in head and neck and lead mainly to the brainstem
Most cranial nerves carry fibers between the brainstem and what receptors and effectors?
Ipsilateral receptors and effectors