2 Major cell types

Neurons: functional unit (generates AP's) Glial cells: non-neuronal cells that support neurons (doesn't generate AP's)

Afferent/sensory division's components - PNS

Somatic sensory, Visceral, Special - All detection of stimuli

Efferent/motor division's components - PNS

Somatic motor (voluntary skeletal muscle), Autonomic motor (smooth/cardiac muscle/glands)(sympathetic, parasympathetic, enteric)

Astrocytes (glial cell) function

- physically support neurons - form BBB - form scar tissue (inhibits regen of severed axons) - recycle neuroT's - maintain electrolyte balance

Gray matter components

unmyelinated cell bodies, dendrites, axon terminals

White matter components

myelinated axons and few cell bodies

Tracts - white matter

bundle of axons connecting different regions of CNS

Protective elements of CNS

- Bone: skull, vertabrae - Meninges: dura, arachnoid, pia mater - CSF - Blood brain barrier

The Meninges + meningitis

dura: tough outer arachnoid: spidery intermediate pia: delicate inner meningitis: infection of meninges

Cerebrospinal Fluid (made by what and how does it travel) + hydrocephalus

1. produced by choroid plexus 2. reabsorbed into venous blood 3. mechanical protection 4. electrolyte balance Hydrocephalus: reabsorption is blocked = accumulation of CSF

Blood Brain Barrier

- provides oxygen and glucose (brain has no glycogen stores) - transports molecules needed for brain

3 main regions of the brain

cerebrum, cerebellum, brainstem

Cerebrum components

Corpus Callosum: nerves that connect R & L hemispheres Cerebral Cortex: outer layer folded into gyri and grooves called sulci

4 major divisions of the diencephalon + functions

Thalamus: integrating center for sensory and motor info Epithalamus: pineal gland (melatonin) Hypothalamus: homeostasis, posterior pituitary (hormones) Subthalamus: movement

Components of the brainstem + functions

midbrain: eye movements, auditory/visual, substantia nigra pons: relay between cerebellum and cerebrum, breathing medulla oblongata: involuntary functions

Cerebellum + functions

- sensory inputs from spinal cord - motor commands from cerebral cortex - motor timing/scaling/coordination/learning - balance/gait - eye movements

Functions of the Limbic System + consists of ____

learning, emotion, appetite (visceral function), sex, endocrine integration Consists of .... - thalamus, hypothalamus, basal ganglia, cingulate gyrus, hippocampus, amygdala

Spinal Cord Functions

- send sensory info from body to brain (dorsal) - send motor commands from brain to body (ventral) - coordinate reflexes (acts w/o signals from brain) - rhythmic movements (walking)

Section of the spinal cord

Dorsal roots: axons of aff neurons enter spinal cord Dorsal root ganglia: cell bodies of aff neurons ventral roots: axons of eff neurons leave spinal cord

Spinal cord gray matter

Horn: gray matter towards outside of spinal cord

Each half of gray matter is divided into....ABC

- dorsal (posterior) horn: cell bodies of interneurons - ventral (anterior) horn: cell bodies of efferent motorneurons supplying skeletal muscle - Lateral horn: cell bodies of autonomic neurons supplying smooth/cardiac muscle and glands

Spinal cord white matter

columns/funiculi: posterior/dorsal, lateral, anterior/ventral columns on each side tracts/fasciculi: subdivisions of each column

Difference between somatic and special senses

somatic: receptors for skin, muscles, joints, fascia, viscera - somatosensory: perception of touch, pressure, pain, temp, position, movement, vibration special: 5 senses, equilibrium (both), sight

Sensation vs. Perception + where is it processed

Sensation: awareness of stimulus Perception: sensation + understanding of meaning both processed in cerebral cortex

T/F: olfactory sensory info passes through thalamus on its way to cerebral cortex

F: goes to cerebrum instead

5 major types of receptors

chemo, mechano, thermo, photo, noic(pain)

2 types of sensory receptors

specialized: endings of diff axons Seperate: respond to stim and transmit via synapses

4 fundamentals of sensory info

1. Modality (stim type) 2. intensity 3. location 4. duration

Neural encoding: modality

- structure of receptor determines modality (labelled line codes = receptor projects along pathway to specific region) types of receptors: - tactile (meissners) corpuscle: light - tactile (merkels): touch - free nerve ending: pain - lamellated (pacinian): vibration and deep pressure - ruffini: warmth and mechano

Neural encoding: intensity

- increased intensity = membrane potential of aff axon increases - increases cause increased AP's (frequency coding) and uses more receptors (population coding) - changes in firing rate encodes stimulus properties (temporal pattern code)

Neural Encoding: Duration

- duration of action potentials in the sensory neuron - slowly adapting (tonic) receptors respond to stimulus the entire time - rapidly adapting (phasic) receptors fire when stimulus first received but stop if strength remains constant (steady state) - ex. cannot smell perfume after a bit The only way to create a new signal is to change intensity of stimulus

Neural encoding: Location

- different modalities travel along specific tracts in spinal cord towards brain - locating a stimulus depends on size/density of receptive field - lateral inhibition (CNS) focuses ascending sensory signals = enhances spatial acuity (can tell apart two different stimulus') Smaller receptive field = greater spatial acuity

Two-point discrimination

better on hands and face and worse on abdomen/proximal parts - density of receptors is higher in places with better 2-point discrimination - SA of sensory cortex is higher

Divergence

each sensory afferent sends branches to many CNS neurons

Convergence

a given CNS neuron receives inputs from many sensory afferents

Somatosensory cortex

recognizes where ascending sensory tracts originate (in parietal lobe)

Cortical association areas

- receives input from primary cortices

Presynaptic inhibition

- reduces transmitter release at synapse between 1st and 2nd order sensory neurons - inhibits specific sensations - lasts several milliseconds

Postsynaptic inhibition

- hyperpolarizes membrane of 2nd order sensory neuron - reduces effect of ALL synaptic inputs (non-selective) - less than 1 millisecond

How does the brain distinguish different types of information?

Labelled Line Codes

Why does phantom limb pain occur?

- somatic receptors receive stimuli, if afferent fibers are stimulated when approaching cortex, it travels the same than if somatic receptors were stimulated directly - after amputation, remaining afferent fibers still transmit like there were specialized to despite having no somatic receptors at beginning of afferent pathway

3 classes of movements generated by motor systems

- reflexes: rapid, involuntary controlled by magnitude of stimulus - rhythmic motor behavior: initiation and termination, voluntary, once activated it becomes reflex-like (ex. walking) - voluntary

3 organizational principles to create movement

- continuous flow of sensory info - hierarchy of control levels (cortical areas = lower level) - parallel systems

High centers that control bodily movement

- form complex plans via command neurons - structures: involved in memory, emotions, motivation, sensorimotor cortex

Middle level that controls bodily movement

- converts higher center plans to many smaller motor programs - transmitted through descending pathways to local control level - Structures: sensorimotor cortex, cerebellum, basal nuclei, brainstem nuclei

Local level that controls bodily movement

- specifies activity of muscles and joints - Structures: brainstem or spinal cord interneurons, afferent/motor neurons

Basal Nuclei/Ganglia

- paired motor and learning functions - receives input from cortex and provides feedback via thalamus - initiates movement - suppresses activity of muscles that would resist the movement - form some of extrapyramidal system - looping parallel circuits (sensorimotor cortex -> basal nuclei -> thalamus -> sensorimotor cortex)

Descending pathways divide into 2 groups

- pyramidal system: voluntary control of muscle, corticospinal (supplies muscles of body)/corticobulbar tracts (supplies muscles of head/neck) - extrapyramidal system: involuntary control, doesn't pass through medullary pyramids

Descending pathways

carry motor info from brain/brainstem to muscles via spinal cord

2-neuron chain structure of descending pathways

- Upper motor neurons: initiates signal from brain, synapse with lower motor neurons in spinal cord or brainstem, originates in primary motor cortex or brainstem nuclei - Lower motor neurons: relays signal to muscle, originates in ventral horn of spinal cord or cranial nerve nuclei in brainstem

where are medullary pyramids located

- white matter structures in medulla oblongata of brainstem

How do signals of extrapyramidal system travel

through the tegmentum of brainstem (contains brainstem nuclei where descending pathways originate)

what does the EEG of a sleeping person look like?

- slower frequency, higher amplitude - theta and delta rhythm - slow wave sleep

what does the EEG of an increasingly drowsy person look like?

- goes to beTa rhythm (alerT)

reticular formation

controls states of consciousness

Declarative Memory (explicit)

retention/recall of conscious experiences that can be put into words - memory of an event (knowing where it happened) - involves: hippocampus, amygdala (limbic system)

Procedural Memory (implicit)

memory for skilled behaviors aka. how to do things - riding a bike involves: sensorimotor cortex, basal nuclei, cerebellum

Consolidation

short term memories become long term memories

retrograde amnesia

short term memory stopped from a blow to the head

anterograde amnesia

lose the ability to consolidate short term memories

Long-term potentiation

synapses undergo increase in effectiveness when heavily used - alters gene expression (new protein synthesis)

Plasticity for memory formation

ability of neural tissue to change from activation

left vs right hemispheres functions

left: produce/comprehend language, conceptualize, speaking/writing, verbal memory right: understan/express emotional aspects of language males only use left side females use both

Broca's area (frontal lobe)

- motor aspects of speech - lesions result in motor aphasia (slurring) but can still understand

Wernicke's area (temporal lobe)

- comprehension of language - lesions result in sensory aphasia (handed a pen, what is it? a spoon, use it? writes her name) - sensory to motor is different than sensory to cognitive

most consistent risk factor for neurodegenerative diseases

age

Dementia

loss of (cognitive function, thinking, reasoning, remembering) - buildup of proteins

Alzheimer's: most common cause of dementia

loss of cholinergic neurons

senile (amyloid) plaques of alzheimers disease

deposits of beta-amyloid protein (between nerve cells), clump together = toxic

neurofibrillary tangles of alzheimers disease

tangles of tau protein inside neuron (cant transport materials)

Parkinson's disease

affects substanitia nigra neurons - affects neurons of pars compacta region: control of body movement and muscle tone

symptoms of parkinsons disease

- parkinsonian gait (slowness - bradykinesia, shuffling, reduced arm swing) - emotionless face - asymmetric resting tremor - instable posture - impaired balance - rigidity - freezing (akinesia)