Chapter 12 Flashcards
Neural tube
Beginning of the nervous system as we think about it.
Gives rise to ventricles and spinal cord
What does the brain look like at 13 weeks and why?
Smooth because cranium hasn’t developed
What does the brain look like at 26 weeks and why?
Ridges and grooves in the brain now
What does the folding of the brain allow?
Have lots of neurons and cell bodies while minimizing total volume within the cranium
Describe gray matter and its properties.
Composed of neuron cell bodies.
Not myelinated.
Interneuron: unmyelinated axon.
Describe white matter and its properties.
Bundles of axons.
Forms tracts that connect parts of brain.
Ascending and descending tracts in the spinal cord.
What are clusters of neuron cell bodies called in the PNS and CNS?
PNS: ganglia
CNS: nuclei
What are bundles of myelinated axons called in the PNS and CNS?
PNS: nerves
CNS: tracts (white matter)
What are the ventricles of the brain connected to?
Each other and the central canal of the spinal cord
What are ventricles lined by? What do they contain?
Lined by: ependymal cells
Contain: cerebrospinal fluid
List the ventricles and how they are connected.
Lateral ventricles are connected by interventricular foramen, which connects lateral ventricles to third ventricle (located in diencephalon).
3rd ventricle is connected to 4th via cerebral aqueduct.
From the 4th ventricle, CSF can go down into the spinal cord.
Define aperture
one way valve
Define ventricles
hollow fluid filled holes
Why are ependymal cells important when lining the ventricles
to produce and absorb CSF in certain areas
Define gyrus, sulcus, and fissure
Gyrus: ridge
Sulcus: separates two gyri. Cortex descends into the sulcus, allows us to package more cell bodies
Fissure: deep sulcus. Not very many
Where is the transverse cerebral fissure?
Separates cerebrum from cerebellum
Where is the frontal lobe?
Anterior to the central sulcus
Where is the parietal lobe?
Posterior to central sulcus
Where is the occipital lobe?
Posterior to the parieto-occipital sulcus
Where is the temporal lobe?
Inferior to the parieto-occipital sulcus
Where is the gyri of insula?
Hidden by the frontal and temporal lobe
What are the three types of functional areas?
Motor areas: control voluntary movement
Sensory areas: conscious awareness of sensation
Association areas: integrate diverse information
Properties of the frontal lobe.
No sensory goes directly to the frontal lobe.
Complex executive function and voluntary motor.
Most dorsal portion of the frontal lobe?
Precentral gyrus (primary motor cortex)
What is anterior to the primary motor cortex?
Premotor cortex
Location of frontal lobe in relation to sulci?
Ventral to the central sulcus and superior to the lateral sulcus.
Properties of the primary motor cortex
Large pyramidal cells of the precentral gyri.
Long axons –> pyramidal (corticospinal) tracts.
Allows conscious control of precise, skilled, voluntary movements.
Motor homunculi
“little man.”
Precentral gyrus.
Fine motor control is in proportion to the size of the body part.
Fine motor control –> lot of small motor units –> larger surface area
Ex. Speech has a lot of motor control
Locations:
- Medial inferior: toes
- Medial superior: legs
- Superior: trunk muscles
- Lateral inferior: tongue and parts of face
- Lateral: thumb and forehead
- Lateral superior: hands
Properties of the premotor cortex.
Controls learned, repetitious, or patterened motor skills.
Coordinates simultaneous or sequential actions.
Involved in the planning of movements that depend on sensory feedback.
Does receive information from the cerebellum.
Properties of Broca’s area.
Present in one hemisphere (dominant; usually left).
A motor speech area that directs muscles of the tongue.
Is active as one prepares to speak.
If you think about saying a word, you activate Broca’s area.
Injury: can still read and understand spoken speech, you just can’t say words. You can still make sounds.
Name the sensory areas
Olfactory cortex
Gustatory cortex
Visceral sensory area
Vestibular cortex
What cortex does the parietal lobe contain?
Primary somatosensory cortex and somatosensory association cortex
What region specifically is the primary somatosensory cortex in?
Postcentral gyrus
Properties of the primary somatosensory cortex
Receives sensory information from the skin, skeletal muscles, and joints.
Capable of spatial discrimination: identification of body region being stimulated.
Where we become aware of the strength or magnitude of the sensory input or even textures.
There is a sensory map in the postcentral gyrus
Properties of the somatosensory association cortex.
Integrates sensory input from primary somatosensory cortex.
Determines size, texture, and relationship of parts of objects being felt.
Processes information.
Store memories and can compare stimuli to certain things, like the difference between a quarter and a nickel based on the ridges.
Location of the somatosensory association cortex.
Posterior to the primary somatosensory cortex
List the visual areas
Primary visual cortex
Visual association area
Properties of the primary visual cortex
Receives visual information from the retinas
Properties of the visual association area
Uses past experiences to interpret visual stimuli (ex. color, form, and movement).
Complex processing involves entire posterior half of the hemispheres.
Makes sense of the information delivered from primary visual cortex.
List the auditory areas
Primary auditory cortex
Auditory association area
Properties of the primary auditory cortex
Interprets information from inner ear as pitch, loudness, and location
Properties of the auditory association area
Stores memories of sounds and permits perception of sounds
Properties of the olfactory cortex.
Region of conscious awareness of odors.
Detect strength or characteristics of odors.
Location of the olfactory cortex
Medial side of the temporal lobe
Location of gustatory center
Insula
Properties of the primary gustatory center
Taste salt and sweet
Parts of the multimodal association areas
- Anterior association area (prefrontal cortex)
- Posterior association area
- Limbic association area
Properties of the multimodal association areas
Receive inputs from multiple sensory areas.
Send outputs to multiple areas, including the premotor cortex.
Allow us to give meaning to information received, store it as memory, compare it to previous experience, and decide on action to take.
Properties of the anterior association area
Most complicated cortical region.
Involved with intellect, cognition, recall, and personality.
Contains working memory needed for judgement, reasoning, persistence, and conscience.
Development depends on feedback from social environment
Properties of the posterior association area
Plays a role in recognizing patterns and faces and localizing us in space.
Involved in understanding written and spoken language (Wernicke’s area)
Properties of Wernicke’s area
Understanding written and spoken language.
Injury: stroke would damage this, and some people would lose the ability to speak or write.
Define lateralization
Division of labor between hemispheres
Define cerebral dominance
Designates the hemisphere dominant for language (left hemisphere in 90% of people)
What does the left hemisphere control?
Language, math, and logic
What does the right hemisphere control?
Insight, visual-spatial skills, intuition, and artistic skills
How do the left and right hemispheres communicate?
Via fiber tracts in the cerebral white matter
What are commissures
Found in corpus callosum.
Connect gray matter of the two hemispheres
What are association fibers?
Connect different parts of the same hemisphere.
Can connect gyri of different lobes but is always in the same hemisphere.
What are projection fibers?
Found in the corona radiata.
Connect the hemispheres with lower brain or spinal cord.
Carry info from the spinal cord up to the thalamus and cortex; carry info from the cortex to the spinal cord; within a hemisphere.
Properties of the Basal Nuclei (ganglia)
Receives info from the cerebellum.
Subcortical nuclei.
Functionally associated with the subthalamic nuclei (diencephalon) and the substantia nigra (midbrain).
Death of cells in substantia nigra (midbrain) is related to huntingtons/parkinsons.
Functions of Basal Nuclei
Influence muscular control.
Help regulate attention and cognition.
Regulate intensity of slow or stereotyped movements.
Inhibit antagonistic and unnecessary movements.
Structures in the diencephalon.
Thalamus
Hypothalamus
Epithalamus
What does the diencephalon enclose?
Third ventricle
Properties of the thalamus.
Relay station and fiber.
Left and right thalamus.
Bunch of nuclei in thalamus and 2nd order neuron.
Filters out weak info, one of two major filters.
Function of the hypothalamus?
Autonomic control center for visceral functions
- ex. blood pressure, rate and force of heartbeat, digestive tract motility
Center for emotional response:
- involved in perception of pleasure, fear, and rage and in biological rhythms and drives.
Regulates body temperature, food intake, water balance, and thirst.
Regulates sleep and sleep cycle.
Controls release of hormones by anterior pituitary.
Produces posterior pituitary hormones.
Where is the epithalamus found?
Most dorsal portion of the diencephalon; forms roof of the third ventricle.
Properties of the pineal gland.
Extends from the posterior border and secretes melatonin.
Melatonin: helps regulate sleep-wake cycles
Properties of cerebral peduncles.
Carry the axons for the descending pathway - corticospinal pathway (pyramidal tracts).
These axons bypass the thalamus
Where is the vision reflux center found?
Superior colliculus in the midbrain
Where is the auditory reflex center located and what is its purpose?
Inferior colliculus in the midbrain.
Determines what side one hears something from.
Properties of the superior cerebellar peduncles.
Carry info from the cerebellum up towards thalamus
Properties of the pons
Continuation of the peduncles.
Some nuclei of the reticular formation: reticular activating system (function). Keeps you awake and filters out extra info.
Regions that control breathing
Properties of the medial lemniscus.
Where the 1st order neuron terminates and synapses on to the 2nd order neuron in the DCML.
Location of the pons.
Forms part of the anterior wall of the fourth ventricle.
Origin of cranial nerves V, VI, and VII.
Sticks out on the ventral side.
Injury to the medulla oblongata
May lose the drive to breathe
Autonomic reflex centers
Cardiovascular center:
- heart rate/force
- blood vessel diameter
Respiratory centers:
- generate respiratory rhythm
- control rate and depth of breathing, with pontine centers
Additional centers regulate:
- vomiting
- hiccuping
- swallowing
- coughing
- sneezing
Pyramids in medulla oblongata
two ventral longitudinal ridges formed by pyramidal tracts
Decussation of the pyramids
Crossover of the corticospinal tracts
Properties of the cerebellum
smooth coordinated muscle contraction.
Proprioception: awareness of body’s position and momentum.
Recognizes and predicts sequences of events during complex movements.
Plays a role in nonmotor functions such as word association and puzzle solving.
Subconsciously provides precise timing and appropriate patterns of skeletal muscle contraction.
Properties of the Limbic System
Emotional or affective brain:
- Amygdala: recognizes angry or fearful facial expressions, assesses danger, and elicits the fear response.
- Cingulate gyrus: plays a role in expressing emotions via gestures, and resolves mental conflict.
- Hippocampus: memory
Puts emotional responses to odors:
- ex. skunk smells bad
Properties of Reticular Formation.
RAS (reticular activating system):
- sends impulses to the cerebral cortex to keep it conscious and alert
- filters out repetitive and weak stimuli (about 99%)
- injury: coma
Motor function:
- help control coarse limb movements
- reticular autonomic centers regulate visceral motor functions: vasomotor, cardiac, respiratory centers
Properties of memory
Storage and retrieval of information.
Two stages of storage:
- short-term memory (STM, or working memory): temporary holding of info; limited to 7 or 8 pieces of information
- long-term memory (LTM) has limitless capacity
Transfer of memory from STM to LTM
Factors that affect:
- Emotional state: best if alert, motivated, surprised, and aroused
- Rehearsal: repetition and practice
- Association: tying new info with old memories
- Automatic memory: subconscious info stored in LTM
Declarative memory (Factual knowledge)
Explicit information
Related to our conscious thoughts and language ability.
Stored in LTM with context in which it was learned.
Nondeclarative memory
Less conscious or unconscious.
Acquired through experience and repetition.
Best remembered by doing; hard to unlearn.
Includes:
- procedural (skills) memory
- motor memory (cerebellum)
- emotional memory (amygdala)
Protection of the brain
Bone(skull): redirects energy away from brain
Membranes (meninges): CSF circulates through these
Watery cushion (cerebrospinal fluid): slows your brain down before it makes contact with the backside of your cranium
Blood-brain barrier: capillaries connected via tight junctions
Function of Meninges
Cover and protect CNS.
Protect blood vessels and enclose venous sinuses.
Contain CSF.
Form partitions in the skull.
Anatomy of the Meninges
Dura mater: outermost layer. dense irregular connective tissue
- Periosteal
- Meningeal: fuses to periosteum
Arachnoid mater: loose thick covering around the brain. has projection fibers that descend towards the brain. dense irregular.
Subarachnoid space: below arachnoid matter. CSF circulates here when outside the ventricles.
Arachnoid villus: valve that allows CSF to move from the subarachnoid space to the vein, known as the sagittal sinus (big vein).
Pia mater: in contact with the cortex. thin delicate layer of connective tissue. gets down into sulci.
Where is CSF produced?
Choroid plexus
Properties of choroid plexuses
Ependymal cells connect via tight junctions in the choroid plexuses.
Capillaries: tiny blood vessels. Walls are simple squamous and all connected via tight junctions.
Nothing passes through without assistance.
CSF is made from blood
Functions of the blood-brain barrier.
Helps maintain a stable environment for the brain.
Separates neurons.
Composition:
- continuous endothelium of capillary walls
- basal lamina
- feet of astrocytes: provide signal to endothelium for the formation of tight junctions
Location of the spinal cord.
Begins at the foramen magnum (hole).
Ends at conus medullaris at L1 vertebra.
Filum terminale: extension of pia mater from conus medullaris. connects to sacrum and keeps tension on spinal cord and keeps it in place.
Cauda equina: “horse’s tail.” spinal nerves that descend within the open region within the vertebral column
Functions of the spinal cord
Provides two-way communication to and from the brain.
Contains spinal reflex centers.
Protection of the spinal cord
Denticulate ligaments: extensions of pia mater that secure cord to dura mater.
Filum terminale: fibrous extension from conus medullaris; anchors the spinal cord to the coccyx.
Where would a spinal tap be done and why?
Around L5, specifically between L4 and L5. You can stick a needle all the way through to the subarachnoid space, where you can obtain a sample of CSF. There is no spinal cord and less spinal nerves, so you are less likely to hit something randomly.
How many spinal nerves are there?
31 pairs
Dermatome:
area of skin innervated by the cutaneous branches of a single spinal nerve.
Most dermatomes overlap, so destruction of a single spinal nerve will not cause complete numbness.
How are dermatomes used medically?
Useful in neurology for finding the site of damage to the spine.
Paraplegia
Injury with loss of lower appendages and/or trunk but not hands/arms.
Tetraplegia
Loss of arms and legs and trunk and/or shoulders
Incomplete spinal cord
either to the left or right of midline, no middle ground
Hemiplegia
Affects one side of the body, including arm, leg, and trunk.
Associated with a stroke.
Injury to primary motor cortex.
Cortex issue.
Paresthesias
Abnormal sensation
Flaccid paralysis
Injury to lower motor neuron.
No voluntary control of muscles.
No reflex activity
Spastic paralysis
Injury to upper motor neurons.
No voluntary control of muscles.
Muscles can be stimulated by reflex activity.
Muscle atrophy delayed.
