BMSC 207 MIDTERM Flashcards
1
Q
What is the definition of physiology?
A
Physiology: The study of the normal functioning of a living organism and its component parts including all its chemical and physical processes.
2
Q
What is the level of organization for the body?
A
Top to bottom is small to big
- Cells: Smallest unit of structure capable of carrying out life processes
- Tissue: Collection of cells carrying out related functions (usually the same type of cells)
- Organ: Formation of tissues into a structural and functional unit
- Organ system: Integrated groups of organs
3
Q
What is an emergent property?
A
- Emergent properties: Properties of a complex system that cannot be explained by a knowledge of a systems individual components (ex. Emotion cannot be explained simply by individual nerve cells)
4
Q
What is the definition of homeostasis?
A
- Homeostasis: The ability to maintain a relatively stable internal environment despite exposure to external variability
- Homeo = Like or similar (range of values)
- Homo = same
- Stasis = Condition (not a static state)
5
Q
What is the law of mass balance?
A
Law of mass balance: If the amount of a substance in the body is to remain constant, any gain must be offset by an equal loss (ex. Water in body)
6
Q
What is the principle of the dynamic steady state?
A
- Dynamic Steady State: The idea that materials are constantly moving back and forth
7
Q
What is the difference between function and mechanism?
A
Distinction between function and mechanism:
- Function: ‘why’ is considered teleological approach
- Ex. Why do RBC transport O2: Because cells need O2 and RBC bring it to them.
- Mechanism: ‘how’ is considered mechanistic approach
- Ex. How do RBC transport O2: O2 binds to Hemoglobin molecules in the RBC
8
Q
What is the Extracellular fluid?
A
ECF: Is a buffer between the cells and the external environment
9
Q
What is the intracellular fluid?
A
ICF: The fluid present within the interior of the cell.
10
Q
What is local control?
A
Local control: The control of a small area and is restricted to the tissues or cells involved
11
Q
What is reflex control?
A
Reflex control: Uses long distance signalling - Any long distance pathway that uses nervous, endocrine or both
- Causes systematic changes in body. But does not kick in until it senses the stimulus is out of range
- Uses feedback loops.
12
Q
What is a negative feedback loop? Is it homeostatic or not?
A
Negative feedback loop:
- Pathway where the response shuts off/ removes the stimulus is negative feedback.
- It IS HOMEOSTATIC
- ex. Blood Glucose level (both increased and decreased)
13
Q
What is a positive feedback loop? Is it homeostatic or not?
A
Positive feedback loops:
- NOT HOMEOSTATIC
- Reinforce a stimulus rather than trying to turn it off.
- requires intervention outside the loop to cease the response.
- Ex. Childbirth/labor
14
Q
What is feedforward control?
A
Feed forward control:
- A few reflexes have evolved that allow the body to predict a change is about to occur
- Ex. Salivating before eating
15
Q
What are biorhythms?
A
- Biorhythms are variables that change predictably and create repeating patterns or cycles of change Ex. Circadian rhythm
- may create an anticipatory response to predictable environment changes.
16
Q
What is a set point?
A
Set point: ‘Normal’ value for accepted criteria (ex. Body temp)
17
Q
What are the functions of membranes in the body?
A
- Physical isolation: barrier cell and environment and between ECF and ICF
- Regulation of change with environment: controls entry and exit and elimination.
- Communication between the cell and its environment: certain proteins allow for responding and interaction with external enviro.
- Structural support: proteins in membrane are used to connect cells and anchor to cytoskeleton.
18
Q
What is the average composition of membranes?
A
Average composition of a membrane is: 55% proteins, 45% lipids, small amount of carbs.
- Membranes have different compositions: the more active the membrane the higher it’s protein content.
19
Q
What are the 3 types of lipids in the membrane? What % do they account for?
A
- Phospholipids: most abundant lipid component in cell membrane 50%
- Sphingolipids: Lipid anchored proteins commonly attached to them 30%
- Cholesterol: Positioned between phospholipid heads to add flexibility and help make membrane impermeable to small water soluble molecules 20%
20
Q
How does the membrane display hydrophobic forces?
A
They are amphipathic.
21
Q
What are integral membrane proteins? What are the functions of integral membrane proteins?
A
Integral proteins:
- include transmembrane and lipid anchored proteins.
Integral membrane proteins: help with membrane receptors, cell adhesion molecules, transmembrane movement (channels, carriers, etc), Enzymes, and mediators of intracellular signalling.
22
Q
What are lipid anchored proteins?
A
Lipid anchored proteins link directly to fatty acid, and have an external GPI anchor (sugar phosphate chain)
23
Q
What are peripheral proteins? What are the functions of peripheral proteins?
A
Peripheral proteins:
- attach to integral proteins, OR loosely attach to phospholipid head.
Peripheral proteins: participate in intracellular signalling, and form sub membrane ours cytoskeleton.
24
Q
What is a lipid raft?
A
Lipid rafts: planar lipid raft - elevated because sphingolipids are longer than phospholipids
- Caveolae: often associated with endocytosis
- Commonly contain proteins
25
What are the two types of membrane carbohydrates?
- Glycoproteins and glycolipids: Cell to cell interactions and forms protective coat called glycocalyx
26
What is the seperaton of body fluid compartments in the body?
- ICF = 2/3 of total body water volume
- ECF = 1/3 total body water volume (consists of interstitial fluid 75% and blood plasma 25%)
- 42kg of 70kg is water
- 60% of the body is water
- Women have lower water percentage because they have more adipose tissue
27
What is the difference between adipose ad skeletal tissue?
- Adipose tissue - contains very little water volume. (Fat cells)
- Skeletal muscle - 75% water 18% protein
28
What is osmosis?
Osmosis: Movement of water in response to a conc’n gradient. (Low - High solute concentration, pretty much freely between compartments - Uses Aquaporin channels)
29
What is osmotic equilibrium?
- Extracellular and intracellular compartments are in osmotic equilibrium - fluid conc’n is equal
- Osmotic equilibrium does not equal chemical or electrical equilibrium
30
What is Osmolarity?
Osmolarity: Number of particles in solution. NOT MOLARITY
molarity(mol/L) x particles/molecule (osmosis/mol)
= Osmolarity (osmol/L)
31
What is tonicity?
Tonicity: Describes the visual change in how a solution affects cell volume when cell is placed in solution and is allowed to come to equilibrium (uses isotonic, hypertonic, hypotonic to describe this change)
32
What is the difference between Osmolarity and tonicity?
- Osmolarity = # of solute particles - compares two solutions
- Tonicity has no units - Depends on the concentration of non-penetrating solutes. Compares solution and a cell
33
What is the difference between Osmolarity and osmolality?
- Osmolarity = osmoles per litre of solution
- Osmolality = osmoles per kg of solvent
34
What is diffusion?
Diffusion: Area off high concentration too an area of low concentration
- No outside energy source
- Continues until concentrations reach equilibrium
35
When does diffusion speed up and slow down?
- Diffusion gets faster when: Along higher concentration gradients, Over shorter distances, At higher temperatures, For smaller molecules, Increased surface area
- Diffusion gets slower When: Lipid solubility varies, Molecule size, increased cholesterol = lower diffusion
36
What are channel proteins?
Channel Proteins: Made of membranes spanning protein subunits. Move smaller substances extremely fast
- Can be:
- Open: leak channels (gate always open)
- Gated channels: normally closed (needs stimulus) Can be - chemically gated, voltage gated, or mechanically gated
- Selectivity determined by: size of pore and charge of AA lining pore.
37
What are carrier proteins?
Carrier proteins: Large complex proteins that change conformation to move molecules.
- Slower (1000-1000000 per sec)
- Can move small organic molecules that cannot pass through channels.
- Can be: Uniport (one type of substance), Symport (two/more molecules the same direction), Antiport (move substrates in opposite directions)
38
What is facilitated diffusion?
Facilitated diffusion: uses channels or carrier proteins
- moves down gradient, is passive, and stops once equilibrium is reached
- sometimes cell will change molecule composition to maintain concentration gradient in order to continue bringing more into the cell.
39
What is active transport?
Active transport: Molecules against their concentration gradient - low to high concentration (requires energy and uses carriers)
40
What is primary active transport?
- Primary Active transport: Energy to move molecules comes from ATP
- ex. Na/K ATPase: 3Na out, 2K in
41
What is secondary active transport?
- Secondary active transport: Uses potential energy from concentration gradient one one molecule to slingshot another molecule against gradient.
- often uses sodium. Ex. Sodium glucose transporter
42
What is the difference between competition and saturation in transporter binding?
Competition: Carrier may have more than one substance to bind and substances compete for spots.
Saturation: Rate of transport depends on concentration and number of transporters.
43
What is Phagocytosis?
- Phagocytosis: Creates vesicles using cytoskeleton (Uses ATP)
44
What is endocytosis?
Endocytosis: Differs from phagocytosis because there is no cytoskeleton movement and vesicles are much smaller. (Also uses ATP)
45
What is pinocytosis? And what is receptor mediated transport?
Pinocytosis: Allows ECF to enter - Nonselective
Receptor mediated transport: Selective process
46
What is exocytosis?
Exocytosis: Vessicles connect with cell membrane and release contents to outside.
- can be continuous or intermittent
47
What is epithelial transport?
Epithelial Transport: Substances moving in and out of the body or moving between compartments.
- Apical and basolateral membranes have different properties
- Lumen to ECF = Absorption
- ECF to lumen = Secretion
48
What is the difference between transcellular, paracellular, and transcytosis epithelial transport?
- Transcelluar: Across epithelial cell (requires energy)
- Paracellular: Between tight junctions
- Transcytosis: Compartments, Congo of Endo, expo, Phago (requires energy)
49
What is the membrane potential?
Membrane potential: The electrical disequilibrium between ICF and ECF is called membrane potential difference or membrane potential (Vm)
50
What is the equilibrium potential?
Equilibrium potential: Membrane potential that exactly opposes the concentration gradient is known as the equilibrium potential. (Eion, ex. Ek or Ena)
- For K: When the concentration gradient is 150mV intracellular lay and 5mV Extracellular, the Ek is -90mV
51
What is the resting membrane potential?
Resting membrane potential: the membrane potential of a cell when it is not active it is usually around -70mV in cells
- Cell membrane is 40 times more permeable to K then Na
52
What is the function of the Na/K ATPase
Na-K ATPase:
- Sets up concentration gradient that determines membrane potential.
- Ensures that the concentration gradients are maintained for cell function to be continued.
53
What are the factors that influence membrane potential?
1. Concentration gradients of ions in membrane: changes in gradient result in alteration of membrane potential (applies to leak channel ions)
2. Permeability of membrane to ions with a concentration gradient (opening gated channels)
54
What is the difference between Afferent and efferent in the nervous system?
- Afferent: Carry’s info to The CNS
- Efferent: info away From CNS
55
What are the cells of the nervous system?
-Neurons: Basic signalling unit of nervous system
- Glia: Support cells
- Cell body: control centre, contains nucleus
- Dendrites: receive info from other cells
- Axon: carry signals from integrating centre to target cells
- Presynaptic terminals: contain transmitting signals.
56
What are the different types of neurons?
Neurons:
- Afferent: sensory - Carry info about temperatures, pressure, light/ stimuli TOO CNS
- Interneurons: complex branching Neurons facilitate communication
- Efferent: Motor - controls skeletal muscles, Autonomic - Influences internal organs (sympathetic and parasympathetic)
- Nerves: Bundles of peripheral Neurons. Can be efferent, Afferent, or mixed.
57
What is axonal transport? What is the difference between anterograde and retrograde?
Axonal transport: Axon is specialized to convey chemical and electrical signals that require a variety of different types of proteins
- Anterograde: Cell body to presynaptic terminal
- Retrograde: Presynaptic terminal to cell body
58
What is Fast axonal transport?
Fast: Membrane bound proteins and organelles (vesicles and mitochondria)
- Antereograde: Cell body to axon 400mm/day
- Retrograde: Axon terminal to cell body 200mm/day
59
What is slow axonal transport?
- Slow: Cytoplasmic proteins (enzymes) and cytoskeleton proteins
- Anterograde, 8mm/day, evidence for retro
- slow due to pausing or larger molecules
60
What are kinesins?
Kinesins: anterograde transport
- positive section of the microtubules
61
What are dyneins?
Dyneins: Retrograde transport
- negative section of microtubules
ATP hydrolysis drives movement of proteins to weak along filaments
62
What are synapses?
Synapses: Space between neurons contains Extracellular matrix that holds pre and post synaptic cells in close proximity. (Looks like open space, is not)
- Increased axon = increased synapses = increased brain size
- Synapses must be maintained through repeated use “use it or lose it”
63
What are glia cells?
Glia cells: Provide support to neurons
- more recently known to be a 1 to 1 ratio with Neurons
- known to communicate with Neurons and provide biochemical support.
64
Myelin forming glia?
65
What is demyelination? What is MS?
Demyelination: Loss or destruction of myelin
Multiple Sclerosis (MS) - Disorder resulting from demyelination in brain and spinal cord
- MS causes: Autoimmune, reduced myelin producing cells, and genetic and environmental factors.
66
What are satellite glial cells?
Satellite glial cells: Exist within ganglia in the PNS, form supportive capsule around the cells bodies of Neurons, supply nutrients, structural support (protective cushion)
67
What are Astrocytes?
Astrocytes: Highly branched glial cells in CNS believed to make up half of all cells in the brain, several subtypes exist.
- Functions: Take up and release chemicals at synapses, provide neurons with substrates for ATP production, maintains homeostasis in ECF, Surround vessels.
68
What are microglia?
Microglia: Specialized immune cells that reside in the CNS, Serves to protect and preserve neuronal cells from pathogens and facilitate recovery from metabolic insults.
- if signals that activate microglia pass threshold, or microglia remain activated past a certain time period, cells start to be detrimental (Alzheimers, ALS, etc)
69
What are Ependymal cells?
Ependymal cells: Line fluid cavities in brain and spinal cord, help to circulate cerebrospinal fluid. (Protection, chemical stability, clearing wastes)
70
What rate ogliodendrocytes?
71
What are Schwann cells?
72
What factors affect membrane potential?
Factors affecting membrane potential:
1. Uneven distribution of ions across cell membrane
2. Membrane permeability to those ions
73
What is the Nernst equation?
Nernst equation: membrane potential that would result if the membrane were completely permeable to only one ion.
74
What is the Goldman-Hodgkin-Katz equation?
Goldman-Hodgkin-Katz equation: predicts membrane potential that results from the contribution of all ions that can cross the membrane. Determined as the combined contribution of each ion to membrane potential.
75
What are the three types of ion channels?
1. Mechanically gated channels - open in response to physical forces. In sensory neurons
2. Chemically gated ion channels - respond to ligands including extracellular neurotransmitters and neuromodulators or intracellular signalling molecules.
3. Voltage gated channels - Respond to changes in membrane potential.
76
What is conductance?
Conductance - Ease which ions floe through a channel
5 types of ion channels: Na channels, K channel, Ca channel, Cl channel, non-covalent cation channel
77
What are channelopathies?
Channelopathies - can disrupt how ions flow through ion channel, can alter channel activation, can alter channel inactivation. (Cystic fibrosis, congenital insensitivity to pain, muscle disorders)
78
What is Ohms law?
Ohms law: Current flow is directly proportional to the electrical potential difference in volts between two points and inversely proportional to resistance. I =V/R
- In a cell: membrane resistance, and internal cytoplasm resistance are present.
79
What is a graded potential?
1. Graded potentials: variable strength signals that travel over short distances and lose strength as they travel. Can be depolarizing or hyper polarizing. Large enough depolarization can induce an action potential.
- Graded because amplitude is directly proportional to the strength of the stimulus and can vary.
80
What is an action potential?
2. Action potentials: brief, large depolarizations that travel for long distances through a neuron without losing strength. Rapid signals over long distances.
- Sequential opening of voltage gated ion channels in the axon membrane as electrical current moves down
81
What types of channels are required for an action potential to occur?
- Voltage gated Na and K channels as well as the leak channels that help set the resting membrane potential.
- Voltage gated Na and K channels are both activated by depolarization, K channels just open more slowly.
82
What are the phases of an action potential?
- Rising phase (depolarization): depolarize good stimuli open voltage gated Na channels, allow Na to travel down electrochemical gradient. At +30mV Na channels inactivate
- Falling phase (repolarization): Voltage gated K channels also open in response to depolarization, but do so more slowly than Na channels causing delayed efflux
- After-hyperpolarization phase (undershoot): Voltage gated K do not immediately close when reaching -70mV
83
Why does a refractory period occur? What are the purposes of a refractory period?
WHY: Na+ contain activation and inactivation gates. Double gating of Na channels creates a refractory period.
PURPOSES:
- Ensures AP travels in one direction
- Limits the rate at which signals can be transmitted down a neuron
84
What is the absolute refractory period and what is the relative refractory period?
Absolute refractory period: Second AP cannot be initiated (1-2msec)
Relative refractory period: a second AP can be initiated but requires a larger than normal depolarizing stimulus (graded potential) (2-5msec)
85
What are the steps of propagating an action potential?
1. Graded potential enters trigger zone
2. Voltage gated Na channels open, Na enters axon
3. Positive charge spreads along adjacent sections of the axon by local current flow
4. Local current flow causes new sections of the membrane to depolarize.
5. Loss of K repolarizes the membrane.
6. Refractory period prevents backwards conduction.
86
What are the factors influencing the velocity of conduction?
1. Diameter of axon: larger axon offers less resistance to current flow, increasing speed.
2. Resistance of the axon to ion leakage: current will spread to adjacent sections more rapidly if it is not lost via leak channels. (Myelin)
- Myelinated = larger diameter, faster (tab key)
-Unmyelinated = smaller diameter, slower (space bar)
87
How do cells communicate?
Neurons communicate at synapses: presynaptic cell (neuron) to postsynaptic cell (neuron, muscle, target cell)
88
What are the two types of synapses?
1. Electrical synapses - some CNS neurons, cardiac muscle, smooth muscle
2. Chemical synapses - majority of neurons in nervous system use these. Lots of Ca is involved. Electrical signals are converted to neurocrine signal.
89
What are neurotransmitters?
- Neurotransmitters: chemical released that acts on postsynaptic cell in close vicinity and causes RAPID response in postsynaptic cell.
90
What are neuromodulators?
- Neuromodulators: Chemical released that acts on a postsynaptic cell in close vicinity that causes a SLOW response in postsynaptic cell.
91
What are neurohormones?
- Neurohormones: secreted into blood and act on targets throughout body.
92
What are ionotropic receptors?
1. Ionotropic receptors: ligand binding to receptors causes a conformational change leading to the opening of a channel. Mediate fast postsynaptic responses (neurotransmitter)
93
What are metabolic receptors?
2. Metabotropic receptors: cytoplasmic tail of receptor is linked to three part membrane transducer protein (g-protein), slower responses (neuromodulators)
- Ligand binding to metabotropic receptor leads to g-protien mediated cellular response.
- can interact directly with ion channels: leads to opening or closing of channel depending on g-protein.
- can interact with membrane bound enzyme: two types
1. Phospholipase C signal transduction pathway: increase in intracellular Ca mediates cellular response (PKC can also mediate cellular response)
2. Adenylyl Cyclades signal transduction pathway: PKA phosphorylates proteins to cause cellular response.
94
How are neurotransmitters released?
- Vesicles containing NTs accumulate in the axon terminal ready to be released. Release occurs via Ca exocytosis.
- Large peptide NTs are produced and packaged into vessicles at some and transported (fast axonal transport)
- Small NTsare synthesized and packaged at the axon terminal (emptyvessicles are trasported from soma or recycled vessicles)
95
How is Neurotransmitter activity terminated?
1. Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells.
2. Enzymes inactivate neurotransmitters
3. Neurotransmitters diffuse from the synaptic cleft
96
What is synaptic integration? What is convergence and what is divergence?
Synaptic integration: one excitatory synaptic event is often not enough to reach threshold in postsynaptic cell.
- Convergence: many presynaptic neurons on one post synaptic neuron
- Divergence: neurons have branching axons that contact many different post synaptic neurons.
97
How does a stronger stimuli affect the neuron?
- Increased AP firing leads to a greater influx of Ca which increases Neurotransmitter release.
98
What is spatial summation?
- Spatial = different location
- Spatial summation occurs when the currents from multiple nearly simultaneous graded potentials combine
- Can be inhibitory or excitatory
99
What is presynaptic modulation?
Presynaptic modulation: excitatory or inhibitory neurons may synapse on terminals (Axo-axon if synapse) and augment communication between pre and post synaptic cell.
- presynaptic inhibition: inhibits NT release
- Presynaptic facilitation: increases NT release
100
What is postsynaptic modulation?
Postsynaptic modulation: synaptic activity CNS be altered by changing the target cells responsiveness to NT. Usually by changing structure, affinity, or number of NT receptors.
101
What is the difference between grey and white matter?
Grey: Consists of unmyelinated somas, dendrites, and axons
White: myelinated axons
102
What is the CNS consisted of?
Brain and spinal cord
103
What is the spinal cord?
Spinal cord: Major pathways for informal flowing back and forth between the brain and the skin, joints and muscles of the body. Each segment gives rise to bilateral pair of spinal nerves, each nerve splits into roots.
- Segments: Cervical (8), thoracic (12), lumbar (5), sacral (5), coccygeal (1)
104
What is a reflex?
Reflex: spinal cord can act as an integrating centre to initiate a response to a stimulus without receiving input from the brain.
105
What is the brain?
Brain: organ providing human species with its unique attributes. 1.4kg, 85 billion neurons containing thousands of synapses.
106
What is the brain stem?
- brain stem: oldest and most primitive region of the brain. Contains 11/12 crainial nerves (not olfactory nerve). Involved in many basic processes in the body including arousal and sleep, muscle tone, coordination of breathing blood pressure regulation and modulation of pain.
107
What is the medulla?
- Medulla: white matter contains all ascending somatosensory tracts and descending corticospinal tracts. Controls involuntary functioning, swallowing, coughing, sneezing, hiccuping, cardiovascular centre, respiratory centre.
108
What are the pons?
- Pons: contains nuclei and tracts. Relays info between cerebellum and cerebrum. Assists medulla in breathing coordination.
109
What is the midbrain?
-Midbrain: junction between lower brain stem and diencephalon. Controls eye movement, relays audio and visual reflexes contains substantial ingrained.
110
What is the reticular formation?
- Reticular formation: extends throughout the brain stem, small clusters of neuronal cell bodies interspersed among tracts. Consciousness, arousal, alertness.
111
What is the cerebellum?
- Cerebellum: processes sensory info related to movement and coordinates the execution of movement. Contains two hemispheres. Sends feedback signals to motor areas of the cerebral cortex, via its connections to. The thalamus and pons helping to correct errors and smooth movements. Posture and balance.
112
What is the diencephalon?
Diencephalon: lies between brain stem and cerebrum. Two main structures.
- Primary structures: thalamus and hypothalamus
- endocrine structures: pineal gland and pituitary
113
What is the thalamus?
1. Thalamus - relay centre, receives sensory info from optic tract, ears, spinal cord and motor info from cerebellum and projects info to cerebrum for processing.
114
What is the pineal gland?
2. Pineal gland - cyclically releases melatonin involved in circadian rhythms and sleep/wake
115
What is the hypothalamus?
3. Hypothalamus - centre for homeostasis, influences autonomic and endocrine function.
116
What is the pituitary?
4. Pituitary
- posterior = neural tissue, extension of brain.
- Anterior = endocrine tissue
117
What its the cerebrum?
Cerebrum: largest and most distinctive part of brain. Two hemispheres divided into 4 lobes connected by corpus collosum.
- gray matter includes: cerebral cortex, basal ganglia, limbic system
- White matter: tracts
118
What is the basal ganglia?
Basal ganglia: three nuclei collectively termed the basal ganglia (nuclei)
- 3 nuclei: globed pallidus, putamen, caudate nucleus
- major job is regulating the initiation and termination of movement.
- receives input from cerebral cortex and provides output to motor portions of the cortex.
119
What is the limbic system?
Limbic system: emotional brain plays a primary role in a range of emotions including pain, pleasure, docility, affection and anger. Also plays a primary role in learning and memory.
- 3 major components: Cingulate gyrus, amygdala, hippocampus
120
What is the cerebral cortex?
Cerebral cortex: outermost layer of cerebrum, is integrating layer of CNS
- 3 specializations:
1. Sensory areas
2. Motor areas
3. Association areas
121
What is a sensory system?
Sensory systems: provide with information about environment outside and inside body. Sensory neurons with a receptor, that converts a physical stimulus into an intracellular signal. Usually with gated channels.
122
What does the dorsal root do?
Carries sensory information (Afferent) information to the CNS
123
What does the ventral root do?
Carries motor (efferent) information to muscles and glands
124
What is a receptive field?
- Size depends on the type of neuron and convergence of multiple neurons onto secondary neurons.
- Convergence creates large receptive fields.
- two stimuli that fall within the same secondary receptive field are precieved as a single point,
- Small receptive fields are found in more sensitive areas.
125
What is Visceral sensory information?
- Conveys information to the CNS about local changes in chemical and mechanical environments of a number of organ systems.
- Information Sid integrated in the brain stem and spinal cord.
126
What is the difference between special senses and somatic senses?
- Special senses have dedicated cortical regions
- Somatic senses integrated in the primary somatosensory cortex
127
What are the four properties of a stimulus?
1. Modality-the physical stimuli being sensed, determined by the sensory receptor being activated,
temperature vs touch receptor and where the pathways terminate in the brain
2. Location
3. Intensity
4. Duration
128
How is the location of a stimulus coded in the brain?
- Coded according to which receptive fields are being activated
- Most sensory stimuli for specific regions of the body are projected to particular areas of the somatosensory cortex.
129
What is population and frequency coding?
Intensity: is determined by the number of receptors being activated (population coding) and the frequency of action potentials coming from those receptors (frequency coding)
130
How is the duration of a stimulus determined?
Duration of stimulus is determined by how long AP’s are being activated
131
What is lateral inhibition?
132
What is the difference between tonic and phasic receptors?
Tonic: slowly adapting receptors that respond for the duration of a stimulus
Phasic: rapidly adapt to a constant stimulus and turn off (stop once stimulus is constant)
133
What makes the sensory pathway specific?
1. Each receptor is most sensitive to a particular type of stimulus.
2. A stimulus above threshold initiates AP’s in a sensory neuron that project to the CNS.
3. Stimulus intensity and duration are coded in the pattern of AP’s reaching the CNS.
4. Stimulus location and modality are coded according to which receptors are activated or (in the case of sound) by the timing of receptor activation
5. Each sensory pathway projects to a specific region of the cerebral cortex dedicated to a particular receptive field. The brain can then tell the origin of each incoming signal.
134
What is the autonomic nervous system?
Involuntary control of smooth muscle, cardiac muscle, many glands, and some adipose tissue.
135
Where does the sympathetic autonomic nervous system originate? Where do the ganglion originate?
Sympathetic:
-ganglia are mainly found in two ganglion chains running along side vertebral column
-preganglionic neurons originate in thoracic and lumbar regions
-short preganglionic, long post ganglionic neurons
136
Where does the parasympathetic autonomic nervous system originate? Where do the ganglion originate?
Parasympathetic:
-preganglionic neurons originate in the brainstem and exit via cranial nerves or from the sacral region of the spinal cord
-ganglia are mainly located on or near their target organs
-long preganglionic, short postganglionic neurons
-cranial nerve X (vagus) contains 75% of all parasympathetic neurons
137
What neurotransmitters are used in the sympathetic and parasympathetic nervous system? What type of receptor is in the postsynaptic neuron?
- Sympathetic: ACh always to a Nicotinic receptor in pre to post synaptic neuron. Norepinephrine most of the time to a adrenergic receptor in post to tissue.
- Parasympathetic: ACh always to a Nicotinic receptor in pre to post synaptic neuron. ACh most of the time to muscarinic receptor in post to tissue
138
Which system is the adrenal medulla associated with?
Adrenal medulla is a specialized neuroendocrine structure
associated with the sympathetic nervous system
-often described as a modified sympathetic ganglion, contain chromaffin cells which are modified postganglionic neurons
139
What do autonomic pathways target?
Target smooth and cardiac muscle, many exocrine glands, a few endocrine glands, lymphoid tissue, liver and some adipose tissue
140
What is an autonomic varicosity?
Autonomic varicosities: Release NT over the surface of target cells. That are the little bubbles that form at the neuroneffector junctions
- The primary neurotransmitters, acetylcholine and norepinephrine can be synthesized in the varicosities
141
What are sympathetic adrenal receptors?
Sympathetic adrenergic (NE and E) receptors are all g-protein coupled receptors (metabotropic receptors)
Two main categories:
- Alpha (most common) and Beta with multiple subtypes
142
What are parasympathetic cholinergic receptors?
Parasympathetic cholinergic (ACh) receptors in target tissues are g- protein coupled receptors: Muscarinic Receptors
5 subtypes M1-M5
143
How does a G protein receptor interact with ion channels?
Interaction with ion channels
-can lead to opening or closing of a channel depending on g-protein (gi, gs)
144
How dies a G protein receptor interact with a membrane bound enzyme?
Interaction with a membrane bound enzyme Two main types:
1. Phospholipase C Signal transduction pathway
-Increase in intracellular Ca2+ mediates a cellular response
-PKC can also mediate a cellular response
2. Adenylyl cyclase signal transduction pathway
-PKA phosphorylates proteins to cause a cellular response
