Physiology I- Midterm 2 Flashcards
The part of a neuron that receives an action potential
Dendrite
The part of a neuron that transmits an action potential
Axon
A side branch of an axon
Collaterals
Located between axon and cell body; neuron trigger zone
Axon Hillock
The part of a neuron that releases chemical messengers; output zone
Axon Terminals
Mylin
- insulates axon (prevents loss of energy)
- made of lipids and proteins
- formed in CNS by oligodendrocytes and in PNS by Schwann Cells
Contiguous Neurons
- unmyelinated fiber
- e.g. digestive neurons
Saltatory Neurons
- myelin sheath with nodes of ranvier between
- energy efficient
- e.g. skeletal neurons (large), urinary neurons (small)
Multiple Sclerosis
- occurs in people who have an inability to form myelin
- signs: fatigue, weakness
- symptoms: vision loss, difficulty walking
- could be caused by environment (cold weather), viruses (i.e. herpes), or a free radical
Synaptic Vesicles
-store neurotransmitter
Synaptic Cleft
between pre and post-synaptic neurons
Excitatory Synapse
creates excitation and action potential
EPSP
Excitatory Post Synaptic Potential
Inhibitory Synapse
- K+ or Chloride cause hyperpolarization
- shuts down post-synaptic neuron to stop action potential from travelling
IPSP
Inhibitory Post Synaptic Potential
5 Steps of Nervous Transmission
- Action potential reaches terminal
- Voltage gated Ca2+ channels open allowing calcium to enter synaptic knob
- Neurotransmitter is released via exocytosis into synaptic cleft
- neurotransmitter binds to receptor site on PSN
- K+ and Na+ channels open in the subsynaptic membrane continuing action potential
Temporal Summation
-two of the same excitatory potentials will add to form larger potential
GPSP
Grand Post Synaptic Potential
Spatial Summation
-two different excitatory potentials will add to form larger potential
How does cocaine effect synaptic transmission?
-blocks re-uptake of dopamine at pre-synaptic terminals
How does tetanus toxin effect synaptic transmission?
-prevents release of inhibitory neurotransmitter GABA affecting skeletal muscles
How does Parkinson’s effect synaptic transmission?
-low dopamine levels
5 Types of Chemical Messengers
- Autocrine
- Paracrine
- Hormones
- Neurocrines
- Cytokine
3 Types of Neurocrines
- Neurotransmitters
- Neurohormone
- Neuromodulator/Neuropeptides
What makes Neuromodulators/Neuropeptides special?
- action occurs over hours, days and years
- used in memory and learning
What are cytokine chemical messengers used in?
- tissue development
- fever (inflammation)
Embryonic CNS Development: Week 3/Day 20
-CNS begins to develop
Embryonic CNS Development: Week 3/ Day 23
-CNS and PNS differentiate
Embryonic CNS Development: Week 4/ Day 28
-forebrain, midbrain, and hindbrain develop
Embryonic CNS Development: Week 6/ Day 42
- forebrain differentiates between cerebrum and diencephalon
- hindbrain differentiates into medulla, pons, and cerebellum
Embryonic Development: Week 11/ Day 77
- cerebrum growth is more rapid than other parts of brain
- looks more human
2 Components of CNS
- Brain
2. Spinal Cord
3 Components of Brain
- Forebrain
- Cerebellum
- Brains Stem
2 Components of Forebrain
- Cerebrum
2. Diencephalon
3 Components of Cerebellum
- Spinocerebellum
- Cerebrocerebellum
- Vestibulocerebellum
3 Components of Brain Stem
- Medulla
- Pons
- Midbrain
2 Components of Cerebrum
- Cortex
2. Basal Nuclei
2 Components of Diencephalon
- Thalamus
2. Hypothalamus
Afferent Neuron
Receptors of Body –> Peripheral Axon –> Central Axon –> CNS
Interneuron
- found in CNS
- 99% of all neurons
- very complex
- abstract phenomenon happen here (learning, motivation, emotions)
- cell body and dendrites–> axon terminals
Efferent Neuron
-cell body –> axon–> target
2 Locations of Efferent Neurons
- Somatic
2. Autonomic
Glial Cells
- “unsung heroes of CNS and PNS”
- neuroglia
- glue
2 Types of Glial Cells in PNS
- Satellite Cells
2. Schwann Cells
4 Types of Glial Cells in CNS
- Oligodendrocytes
- Astrocytes
- Microglia
- Ependymal Cells
Satellite Cells
- form a capsule
- ganglia/ nuclei
Schwann Cells
- form myelin
- provides neurotrophic
Oligodendrocytes
- form myelin
Microglia
- small gluing cells
- scavengers
- stationary until activated
- destroy foreign particles in brain
Astrocytes
- star shaped
- form tight junctions
- secrete paracrine signals leading to BBB
- provide neurotrophic factors
Ependymal Cells
- epithelial cells lining cavities of brain
- instrumental in secretion of CSF
- neural stem cells producing new neurons
Glioma
tumor in brain that is nearly untreatable
Overactive microglia can cause…
- worsening of MS
- Dementia
- Alzheimer’s
- Stroke
3 Components of Meninges
- Dera Matter
- Arachnoid Matter
- Pia Matter
Dera Matter
- closest to brain
- rich in venous system
Arachnoid Matter
-contains sub-arachnoid spaces which fill with fluid that goes back into the venous system through arachnoid villi which draw out anything that needs to go back to the venous system
Pia Matter
- thinnest layer
- contains arteries which provide nutrients and oxygen to brain
Meningitis
- bacterial infection affecting one or all of the three layers which can kill or paralyze
Cerebral Spinal Fluid (CSF)
- made by ependymal cells lining choroid plexus (3rd and 4th ventricle)
- produces 3x per day
- bathes neural tissue and fills subarachnoid space
- high Na+ content (for nerve transmission)
- provides physical support for brain through buoyancy
- shock absorber
How often and how much CSF does the body produce in a day
- 3x per day
- 125-150mls
Blood Brain Barrier (BBB)
- produced by astrocytes
- substances can cross only with transporters
Were is the BBB absent and why?
- vomiting centre (medulla longata) and hypothalamus
- allows imbalances and particles to be sensed and expelled/fixed
What is Parkinson’s caused by, what are the symptoms, and what is the treatment and why?
- caused by lack of dopamine
- shuffling gait
- L-dopa used as treatment because dopamine will not pass through the BBB
Cerebrum
- two hemispheres
- split by corpus collosum
- surface is highly convoluted
- consists of white (one layer, myelinated) and grey matter (6 layers, unmyelinated)
4 Parts of Cerebrum
- Occipital- vision
- Temporal- sound
- Parietal_ sensory stimuli
- Frontal- voluntary activity, elaboration of thought, spoken language
Somatosensory Cortex
- directly behind central sulcus
- point where senses are relayed to
What areas of the body have the most somatosensory cortex allocated to them?
- tongue
- lips
- face
- hand
- genetilia
Motor Cortex
-point where motor signals are sent from
What ares of the body have the most motor cortex area allocated to them?
- mouth
- thumb
- fingers
- tongue
- lips
Cerebral Dominance: Right vs Left Brained
- right- non-verbal skills, dream imagery, artistry, philosophy, spatial skills, wholistic world view, creators, often left handed
- left- language, math, logical, analytical, sequential analysis, detailed thinkers, generally right handed
Wernike’s Area
- understanding language
- located between occipital, temporal, and parietal lobes
Brocha’s Area
- located in front of central sulcus in frontal lobes
- forms words (speech)
Stroke affecting Wernike’s Area
- can’t comprehend spoken language
- receptive aphasia
Stroke affecting Broca’s Area
- comprehension intact
- cannot form words
- expressive aphasia
3 Association Areas
- Prefrontal Association Cortex
- Parietal-Temporal-Occipital Association Cortex
- Limbic Association Cortex
Prefrontal Association Cortex
- personality traits
- decision making
- working memory
Working Memory
stores data and makes decisions based on it
Parietal-Temporal-Occipital Association Cortex
- gives complete picture of your body
- see, hear, sense
Limbic Association Cortex
- memory
- emotion
- motivation
Basal Nuclei
- suppresses unwanted movements encourage useful motor activity especially posture and support
- “refiner”
- receives stimulus from thalamus “relay centre”
Huntington’s Disease
- genetic
- fatal
- affects neurons
- decline in motor activities
- lose in nervous activity leading to dementia (early 20’s)
- loss of cognition
Hypothalamus
- brain area most involved in regulating internal environment
- controls many homeostatic functions
- around 1% of the brain and two glands
Thalamus
- collection of nuclei
- crude awareness of motor activity
- relay station
- site of sensory processing (minus olfactory)
- sends refined sense to higher sensory cortex
Pineal Gland
- located in thalamus
- secretes melatonin and affects circadian rhythm
ADH
- anti-diuretic
- regulates blood pressure
Hormones secreted by Anterior Pituitary
- Gonads (progesterone, testosterone)
- Mammary
- Metabolism
Hormones Secreted by Posterior Pituitary
- Oxytocin (for birth and milk)
2. ADH
Spinocerebellum
- muscle tone
- skilled activity
- middle management
Cerebrocerebellum
- planning activity
- procedural memories
- repeated learning
- motor memory
Vestibulocerebellum
- eye
- balance
- inner ear
Brain Stem
- primitive
- reticular activating system
- 12 pairs of nerves
- life giving/sustaining functions: BP, sleep/arousal, cardiovascular center
Medulla
- BP
- breathing
- vomiting
Pons
- bridge between lower and upper brain
- breathing
- eye movements
- auditory responses
Midbrain
- most primitive
- does not change from week 3 of gestation onwards
CNI
olfactory
CNII
Optic Nerve
CNX
- vagus nerve
- thoracic region
- heart and tongue
Limbic System
- specialized region within forebrain
- emotions
3 Components of Limbic System
- Cingulate Gyrus
- Amygdala
- Hippocampus
Cingulate Gyrus
-some fear
Amygdala
- almond shaped
- controlling of fear
- aggression
- rage
- sex drive
Hippocampus
- neuronal stem cells
- only site where new neurons are produces
- learning and memory
- here and now memory (what, who, where, people, places)
Alzheimer’s
- caused by genetic mutation in hippocampus
- loss of cholinergic neurons causing lack of Acetyl-choline
- old age disease (65% of cases over age of 65)
5 Types of Reflexes
- Cranial
- Innate
- Acquired
- Monosynaptic
- Polysynaptic
Cranial Reflex
-brain or spinal cord
Innate Reflex (3 examples)
- Babinski’s Reflex- stroke sole of child’s foot (toes curl-negative, or flex- positive)
- Sucking- in babies; disappears over time
- Landeau- 2-18 yrs
Acquired Reflex
-e.g. toilet training
Monosynaptic
-stretch
Polysynaptic
-withdrawal reflex
Transduction
conversion of one energy form to another
Perception
nervous input + memory + knowledge
Generators vs Receptors
-generators directly receive stimulus while receptors receive stimulus and transmit it across a synaptic cleft via neurotransmitters to the afferent neuron
Does pain stimulus require a receptor or generator?
Receptor
Ionic Adaptation
- fire until stimulus is removed
- e.g. proprioreceptors and baroceptors
Phasic Adaptation
- rapid adaptation to stimulus
- fire rapidly, resting potential, then hyperpolarization called of response
- e.g. touch or tactile receptors
- anything you sense but then get used to (olfactory)
Large Field Acuity
one point discrimination, sent off as one signal
Small Field Acuity
two point discrimination, sent off as two separate signals
Lateral Inhibition
- capacity of an excited neuron to reduce the activity of its neighbors
- disables the spreading of action potentials from excited neurons to neighboring neurons in the lateral direction.
Free Nerve ending Corpuscles
- superficial
- myelinated or unmyelinated
Meissner’s Corpuscles
- respond to fluttering and stroking movements
- light touch like air movement
Ruffini Corpuscles
- deeper
- respond to skin stretch and deformation
- apply continuous pressure in order to feel them
Merkel’s Corpuscles
- “touch dones”
- tissue displacement
Pacinian
- vibration
- transient touches
- most well-known corpuscles
- used in electrical machines in physio
Fast Pain Receptors
- myelinated
- small
- A-Delta
- 6-30 m/s
- first part of any pain signalling
- sharp stabbing pain
Slow Pain Receptors
- dull aching pain
- second part of pain
- lasts much longer
- unmyelinated fibers
- C-fibers
- 1-2 m/s
A-Beta
- pain control
- inhibits pain
Somatic Pain
- after intense exercise
- do not need pain killers
- should go away on its own within a few hours
Referred Pain
- pain in the internal organs that is felt elsewhere
- e.g. heart pain felt in left arm/shoulder
Pathological Pain
- long-term
- chronic
Phantom pain
- felt in amputees missing limbs
- theory is that little neurons develop and fire at stump
2 Neurotransmitters
- Substance P
2. Glutamate
Substance P
- named for pain?
- secreted by first order neuron
- stimulates second order neuron
- e.g. asprin, morphine, endogenous piatis, endorphins, enkephalins, and dynorphins
Glutamate
- has two receptors
- receptor a. opens calcium channels causing hypersensitivity
Nociception
pain reception
Lens
- transparent
- separates two chambers of eye (posterior and anterior)
- apoptosis
Anterior Chamber
- filled with aqueous humor
- drain by canal of schlemm
Cause of Glaucoma
- lack of draining via canal of schlemm in anterior chamber
- puts pressure on nerves and eventually destroys optic nerve
Aqueous Humor
plasma-like fluid
Posterior Chamber
-filled with vitreous humor
Vitreous Humor
- gel-like
- gives eye it’s shape
- “glassy” looking
Sclera
- transparent
- within posterior chamber
Cornea
-transparent
Choroid
- pink area just inside sclera
- within posterior layer
Ciliary Body
- produces aqueous humor
- formed by choroid layer when it enters the anterior chamber
Iris
- pigment
- even more accurate at identification than DNA
- unique
- very thin
Pupil
- small opening
- allows light to enter the eye
- size of opening determines how much light can come in and out
Retina
-photo receptors
Optic Disc
-contains optic nerves
Fovea
- layers of the retina spread aside
- let light fall directly on the cones
- give the sharpest image
Macula
-region surrounding fovea
Degeneration of Macula causes…
- donut vision
- peripheral vision only
CNII
optic nerv
CNIII
ocular motor nerve
CNVII
tear production (facial nerve)
CNVI
abducens- outward gaze
Emmetropia
- no refractive error
- 20/20 vision
In a healthy eye cilliary muscles are relaxed when _____ and contracted when _______.
- the eye is looking at something far away (flat lens)
- the eye is looking at something close (round/taught)
Myopia
- difficulty seeing far
- most common
- light falls in front of retina
- corrected by concave lens
Astigmatism
-unequal focus with your eyes
Hyperopia
- difficulty seeing near
- less common
- corrected by convex lens
- light falls behind retina
Presbyopia
- difficulty focusing up close
- centre of lens starts to wear
- becomes worse with age
- corrected with bifocals
Rods
- 100 million
- black and white/greyscale
- low acuity
- night vision
Cones
- 3 million
- high acuity
- day vision
- red, green, and blue (high to low wavelength)
Colour Blindness
- affects cones
- more prevalent in males
- linked to X chromosome
- due to damage/lack of red/green cons (higher wavelength)
Dark Photons
Rhodopsin Inactive–> CGMP increases–> Na+/K+–> Inhibitory neurotransmitter–> darkness
Light Photons
Rhodopsin Active–> activation of G Protein transduction–> Enzyme Phosphodiesterase –> CGMP deceases –> inhibitory neurotransmitters decrease –> bipolar graded potential –> ganglion cell action potential –> optic nerve action potential
Light to Dark Adaptation
rods become less adapted
Dark to Light Adaptation
- cones become dislodged
- momentarily blurry
Roles of Ganglion Cells
- very complex
- increases acuity
- increased lateral inhibition
- creates, borders, curves, and sharpens colours
- increases sensation
