Chapter 3: STRUCTURES AND FUNCTION OF THE CNS Flashcards
What are the two subdivisions of the forebrain?
Telencephalon and diencephalon
What does the telencephalon include?
- Most of 2 symmetrical cerebral hemispheres, which make up the cerebrum
- Principal structures of the cerebrum: cerebral cortex, basal ganglia, limbic system
What is the cerebral cortex what is it’s appearance?
- surrounds the cerebral hemispheres
- Appears folded, convoluted: it has sulci (small grooves), fissures (large grooves) and gyri (bulges between adjecent sulci or fissures)
- Enables it to be wider but more concentrated
- Has a grey appearance (gray matter): because cell bodies predominate.
What are the four lobes of the cerebral cortex? (see diagrams for locations)
- frontal lobe
- parietal lobe
- temporal lobe
- occipital lobe
What are the three areas of the cerebral cortex that receive information from the sensory organs?
The whole is called the sensory cortex and consists of three areas:
- primary visual cortex
- primary auditory cortex
- primary somatosensory cortex
What are the functions of the three parts of the sensory cortex?
- Primary visual cortex: receives visual information
- Primary auditory cortex: receives auditory information
- Primary somatosensory cortex: receives information from the body senses except olfaction and gustation
What is the sensory association cortex and what does it do?
- Associates sensation and action: perceiving, learning, remembering, planning, acting.
- Receives information from primary sensory areas
- Rostral region: movement-related activities.
- Caudal region: perceiving and learning.
What happens if someone has damage to the somatosensory association cortex?
- Deficits related to somatosensation and the environment in general
- ex: difficulty perceiving the shape of an object they touch (but they can if they just look at it), trouble drawing maps or following them
What does the primary motor cortex do ?
- movement
- located in front of the primary somatosensory cortex
- neurons in different parts of body connected to different locations of the motor cortex
What does the motor association cortex do? (also called premotor cortex)
- planning and execution of movements
- located rostral to the primary motor cortex
What does the prefrontal cortex do?
- region of the fontal lobe rostral to the motor association cortex
- formulation of plans and strategies
What does lateralization in the cerebral cortex mean?
- the 2 hemispheres cooperate, but do not perform the same functions
- Some functions are lateralized, located primarly on one side of the brain
What is the left hemisphere specialized in?
- analysis of information
- good at recognizing serial events and controlling sequences of behavior
- example: talking, understanding speeches, reading, writing.
What is the right hemisphere specialized in ?
-synthesis: putting isolated elements together, perceiving things as a whole.
What does the corpus callosum do ?
- connects the right and left hemispheres
- perception and memories unification
What is the limbic system formed of?
- limbic cortex (includes the cingulate gyrus)
- hippocampus
- amygdala
What is the fornix?
-bundle of axons that connects the hippocampus to other regions of the brain including the mammillary bodies
What are the mammillary bodies?
-protrusions on the base of the brain that contain part of the hypothalamus.
What is the role of the limbic system?
-learning, memory and emotions
What is the basal ganglia?
- Collection of nuclei below the cortex
- nuclei= groups of neurons of similar shape
What are the three main parts of the basal ganglia, and what is its function?
- 3 parts: caudate nucleus, putamen, globus palladius
- Involved in control of movement (ex: Parkinson’s)
What is the diencephalon and what are it’s 2 major structures?
- second major division of forebrain that surrounds the third ventricle
- Thalamus and hypothalamus
How does the thalamus work what is its function?
- has two lobes
- Divided into several nuclei
- Most neural input to the cerebral cortex is received from the thalamus.
- Projects information to specific regions of cerebral cortex and receives information from it
What are examples of thalamic nuclei and what are their functions?
- lateral geniculate nucleus: receives information from the eye and sends axons to the primary visual cortex
- medial geniculate nucleus: receives information from the inner ear and sends axons to the primary auditory cortex
- ventrolateral nuclei: receives information from the cerebellum and projects it to the primary motor cortex.
What does the hypothalamus do?
- Controls the ANS (Autonomic Nervous System) and the endocrine system
- Organizes behaviors related to the survival of species (fighting, escape, eating, and reproduction)
What is the optic chiasm?
An X-shaped connection between the optic nerves, located below the base of the brain, just anterior to the pituitary gland.
What is the anterior pituitary gland?
endocrine gland whose secretions are controlled by the hypothalamic hormones.
How are hypothalamic hormones produced?
-Secreted by neurosecretory cells.
What is the posterior pituitary gland and how does it work?
- endocrine gland that contains hormone-secreting terminal buttons of axons whose cell bodies lie within the hypothalamus
- secretes oxytocin and vasopressin (secretion controlled by the hypothalamus)
What are the functions of oxytocin and vasopressin?
-number of different physiological and behavioral functions such as pair bonding and parental behavior.
How is the midbrain (also called mesencephalon) structured?
The tectum and the tegmentum
How is the tectum structured?
- located on the dorsal portion of the mesencephalon
- 2 principal structures: superior colliculi and inferior colliculi
What are the functions of the superior and inferior colliculi?
- superior: part of the visual system
- inferior: part of the auditory system
What does the tegmentum consist of?
- Portion of the mesencephalon beneath the tectum
- Includes:
- the rostral end of the reticular
- several nuclei controlling eye movement
- the periaqueductal gray matter
- the red nucleus
- the substantia nigra
- the ventral tegmental area
What is the reticular formation?
- large structure consisting of many nuclei
- receives sensory info by various pathways and projects axons to the cerebral cortex, thalamus and spinal cord.
- Plays a role in sleep, arousal, attention, muscle tone, movement and various vital reflexes.
What is the periaqueductal gray matter?
-contains neural circuits involved in species-typical behavior such as fighting or mating.
What is the red nucleus?
-large nucleus of the midbrain that receives input from the cerebellum and motor cortex and sends axons to motor neurons in the spinal cord
What is the substantia nigra?
A darkly stained region of the tegmentum that contains neurons that communicate with the caudate nucleus and putamen in the basal ganglia.
How is the cerebellum structured?
- covered by cerebellar cortex
- has a set of deep cerebellar nuclei (receives projections from cerebellar cortex and send projections to other parts of the brain)
- each hemisphere attached to the pons by 3 bundles of axons : superior, middle, and inferior cerebellar peduncles
What is the function of the cerebellum?
- receives visual, auditory, vestibular, and somatosensory information.
- receives information about individual muscles movements
- exerts a coordinating and smoothing effect on the movements
What does cerebellar damage result in ?
jerky, poorly coordinated, exaggerated movements, and even difficulties to stand.
What does the pons do ?
- contains part of the reticular formation, including nuclei important for sleep and arousal.
- contains a large nucleus that relays information from the cerebral cortex to the cerebellum
What is the medulla oblongata?
- Main structure of the myelencephalon
- contains part of the reticular formation including nuclei that controls vital functions (regulation of the cardiovascular system, respiration, skeletal muscle tone)
How is the spinal cord structured?
- Protected by a vertebral column: composed of 24 vertebrae
- 2/3 as long as vertebral column
- Other 1/3 is filled by spinal roots composing the cauda equina.
What are the different types of vertebrae?
- cervical (neck)
- thoracic (chest)
- lumbar (lower back)
- sacral and coccygeal (fused vertebrae located in the pelvic region)
What is a caudal block?
The anesthesia and paralysis of the lower part of the body produced by injection of a local anesthetic into the cerebrospinal fluid surrounding the cauda equina.
What are the functions of the spinal cord?
- distributes motor fibers to the effector organs of the body (glands and muscles)
- collects somatosensory information for the brain
- contains some reflex circuits
