M8-9 - Exam #4 - A&P I

Divisions of the brain

Cerebrum, diencephalon, cerebellum, brainstem

Cerebrum

• R/L hemispheres; 5 lobes

• Higher order functions

• Grey matter superficial (cell bodies)

• White matter deep (axons)

Diencephalon

• includes thalamus, hypothalamus

• Relay station, homeostasis, biological rhythms

Cerebellum

• R/L hemispheres

• Planning and coordination of movement

• Tracts converge with brainstem

• Expectation vs outcome (i.e can’t tickle yourself)

Brainstem

• consists: midbrain, pons, medulla

• Basic life functions, homeostasis, some reflexes, integrate/relay information

• Brainstem damage = fatal

Spinal cord

• from foreman magnum to L1/L2 vertebrae

• White matter superficial, grey matte deep

• Reversed

• Central canal-filled with CSF

Neutral tube

• Very early in development

• caudal end → spinal cord

• Cranial end → 3 primary brain vesicles: forebrain, midbrain, hindbrain

• Cavity → ventricles (brain) and central canal (spinal cord)

Primary brain vesicles

• 5 secondary brain vesicles

• By 5th week of development

• Forebrain, midbrain, hindbrain

Secondary brain vesicles

• tell dad me met my spouse

• Telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon

Structures of the mature brain

• cerebrum, diencephalon, brainstem (midbrain), brainstem (pons), cerebellum, brainstem (medulla oblongata)

• Coffee drinks boosts mind power, calmness

Cerebrum anatomical features

• Gyro

• Sulci

• Fissures

Gyro

• elevated ridges (bumps)

• Pre central and post central

Sulci

• shallow grooves

• Central sulcus

Fissures

• Deep grooves

• Longitudinal fissure - separating R/L

• Lateral fissure - separated frontal from temporal lobe

Cerebrum lobes

Frontal, parietal, temporal, occipital, insula

Frontal lobe

• planning and executing movement

• Complex mental functions such as behavior, conscience, and personality

Parietal lobe

• processing sensory information

• Attention regulation

• Hemi-spacial neglect

• Separated by central sulcus from frontal

Temporal lobe

• hearing, language

• Memory emotions (deeper regions)

• Separated by lateral fissure

Occipital lobe

Vision

Insula

• deep within lateral fissure

• Taste, visceral sensations

Motor areas

Contain upper motor neurons

Primary motor cortex

Execute motor activity; precentral gyrus; part of cerebrum

Motor association areas

Planning/coordination of movement (e.g premotor cortex); part of cerebrum

Primary somatosensory area (S1)

Receives info about touch, proprioception, pain, temp; post central gyrus; part of cerebrum

Somatosensory areas

• primary somatosensory area (S1)

• Somatosensory association cortex (S2)

• Part of cerebrum

Special senses

• 5 senses

• Primary visual cortex - occipital lobe

• Primary auditory cortex - superior temporal lobe

• Part of cerebrum

Broca’s area

• production of speech sounds; anterolateral frontal lobe

• Non fluent brocas aphasia

• Broken speech, makes sense

• Part of cerebrum

• Higher order functions

Wernicke’s area

• ability to understand language; temporal lobe

• Fluent aphasia - Wenicke’s aphasia

• Very fluent, but makes no sense

• Part of cerebrum

Basal nuclei

• cluster of cell bodies deep within each cerebral hemisphere

• Involved in movement

• 3 structures: caudate, putamen, globus pallidus

• Part of cerebrum

Limbic system

• hippocampus, amygdala, cingulate cortex, parahippocamus gyrus

• Emotional behavior and memory (emotional memory, PTSD)

Diencephalon components

• thalamus

• Hypothalamus

• Epithalamus

• Subthalamus

Thalamus

• relay station for sensory information

• Controls what input should continue to cerebral cortex

Hypothalamus

• homeostasis, autonomic nervous system, thirst/hunger, sleep/wake cycle

• Control pituitary gland

• Maxillary bodies - input from hippocampus; memory regulation and behavior

Epithalamus

Pineal gland; secrete melatonin (sleep/wake cycle)

Subthalamus

Works with basal nuclei to control movement

Brainstem

• consists of midbrain, pons, medulla

• Throughout:

  • Cranial nerve nuclei

  • Nuclei of reticular formation

  • White matter tracts

Midbrain

• superior and inferior colliculi - visual and auditory processing, respectively

• Substantia nigra - works with basal nuclei to control movement

Pons

Pontine nuclei; regulation of movement/posture, breathing, sleep/arousal

Medulla oblongata

• pyramids: tracts of upper motor neuron fibers

• Nucleus gracilis and cuneatus; nuclei for sensory info

Reticular formation

• regulates alertness and conscience

• Sleep vs wakefulness

• Attention, focus on relevant stimuli, and ignore background

• Mood, drive/motivation

• HR, BP, respiration rate

Cranial meninges

• 3 layers

• Dura mater: thick, double (superficial)

• Arachnoid matter: weblike

• Pia mater: thin, permeable (deepest)

Cerebrospinal fluid

• cushions brain, buoyancy, removes wastes

• Filling ventricles of the brain and central canal of spinal cord

  • 4 ventricles [lateral (1-2), 3rd, 4th]

  • Connected (interventricular formen, cerebral aqueduct)

  • Lined with ependymal cells

Blood-brain barrier

• protects brain from chemicals and disease-causing organisms sometimes found in blood

• Astrocytes and tight junctions between endothelial cells

Homeostasis of vital functions

• primarily controlled by hypothalamus (master regulator)

  • Receives diverse range of inputs (viscera from internally, limbic system, etc)

  • Respond to physiological and emotional changes

  • Adjust output to maintain homeostasis

  • Often instruction to nuclei in reticular formation

    • BP, respiration rate

Circadian rhythms/biological “clock”

• controlled by hypothalamus

• Info on light levels from retina → SCN (hypothalamus) → VLPO (hypothalamus)

• VLPO stimulate pineal gland to release melatonin and lower activity of reticular formation

prefrontal cortex

• character, personality

• awareness of self - theory of mind

• control of behaviors, pro-social, emotional regulation

• problem-solving, decision-making

short-term memory

• working memory

• seconds to minutes; allows you to remember and manipulate information with goal in mind

long-term memory

more permanent form of storage for days, weeks, or lifetime; stored in cerebral cortex

consolidation

process of converting short-term memory into long-term memory; requires hippocampus

long-term potentiation (LTP)

• mechanism for encoding long-term memories

• increases strength of synapse between associated neurons

executive control and external attention?

internal resources → external

episodic retrieval and mental reconstruction?

memory → re-picture in mind

grey matter of spinal cord

• cell bodies

• ventral (anterior) horn - motor neurons

• dorsal (posterior) horn - sensory neurons

• lateral horn - only in thoracic/lumbar regions, autonomic nervous system neurons

white matter in spinal cord

• bundles of axons; ascending and descending tracts

• posterior columns

• anterolateral system

• corticospinal tract

posterior columns

• white matter of spinal cord

• 2 tracts: fasciculus gracilis (medial) and fasciculus cuneatus (lateral)

• touch and proprioception info

• gracilis = lower body

• cuneatus = upper body

anterolateral system

• white matter of spinal cord

• spinothalamic tract (spine → thalamus; ascending)

• pain and temperature

corticospinal tract

• white matter of spinal cord

• motor from primary motor cortex

• cortex → spine; descending = motor

spinal nerves

• bundles of axons

• PNS, to/from spinal cord

• dorsal/posterior root: sensory neuron axons

• ventral/anterior root: lower motor neuron axons

• cauda equina: bundle of nerve roots extending inferiorly

dorsal column medial lemniscus system (DCML)

• sematosensation

• touch and proprioception

• 1st order neuron: detect stimulus, enter dorsal root, ascends posterior columns, synapse at 2nd order neuron

• 2nd order neuron: in nucleus gracilis/nucleus cuneatus of medulla, decussates (cross over), ascends medial lemniscus, synapse at 3rd order neuron

• 3rd order neuron: in thalamus, synapse at S1

anterolateral system

• somatosensation

• pain and temp

• 1st order neuron: detect stimulus, enter dorsal root, immediatly synapses at 2nd order neuron

• 2nd order neuron: in dorsal horn of spinal cord, decussates (crosses over), ascends spinothalamic tract, synapse at 3rd order

• 3rd order neuron: in thalamus, synapse at S1

primary somatosensory cortex (S1) in post central gyrus

• sensory homunculus

• each part of body is represented by specific region of S1 (somatotopy)

• more cortical space dedicated to more sensitive regions

corticospinal tract

• voluntary movement; start in cortex → spinal cord

• upper motor neuron: in primary motor cortex (M1)

  • descends tract

  • decussates at medullary pyramids

  • continues to descend lateral tract

  • synapse at lower motor neuron

• lower motor neuron: in ventral horn of spinal cord

  • exits ventral root

  • synapse at muscle fiber

primary motor cortex (M1) in precentral gyrus

more cortical space, more fine motor control

basal ganglia

• also basal nuclei; motor area

• modify activity of upper motor neurons to allow voluntary movements and inhibit involuntary ones

cerebellum

• motor area

• monitors ongoing movements and determines motor error - difference between intended movement and actual movement

• communicates with upper motor neurons to reduce error (motor learning)

PNS

• sensory/afferent

• motor/efferent

  • somatic - voluntary

  • autonomic - involuntary (sympathetic/parasympathetic)

remember: ganglia = ?

cell bodies in PNS

spinal nerves and peripheral nerves

• originate from spinal cord; innervate structures below head/neck

• ventral/anterior root: motor neuron axons

• dorsal/posterior root: sensory neuron axons

• posterior root ganglia: sensory neuron cell bodies

• posterior and anterior roots fuse to form spinal nerve

• 31 pairs of spinal nerves, all mixed nerves

cranial nerves

• 12 pairs of nerves

• directly to brain

• mostly innervate structures in head and neck

• can be sensory only, motor only, or mixed

olfactory (I)

sensory only; sense of smell

optic (II)

sensory only; vision

oculomotor (III), trochlear (IV), abducens (VI)

motor only, innervate extraocular muscles

trigeminal (V)

both sensory and motor; facial sensation; muscles of mastication

facial (VII)

both sensory and motor; taste from anterior 2/3 of tongue; muscles of facial expression

vestibulocochlear (VIII)

sensory only; sense of hearing and balance

glossopharyngeal (IX)

both sensory and motor; taste from posterior 1/3 of tongue; swallowing movements

vagus (X)

both sensory and motor; widely distributed throughout body

accessory (XI)

motor only; movement of shoulders (shrugging)

hypoglossal (XII)

motor only; movement of tongue