Bios 355 Flashcards
Peripheral nerves
Efferent nerves
Autonomic nerves
Control everything but skeletal muscle
Sympathetic and parasympathetic branch
Somatic motor neurons
Control skeletal muscle Single neuron Always excitatory Forms neural and muscular junction NT is always Ach Target muscle expresses nicotinic cholinergic receptors No varicosities Neuromuscular junction is the synapse of a somatic motor neuron on a muscle fiber
Pre-ganglionic neurons
Can have many collateral axons that stimulate many post-ganglionic neurons
Sympathetic branch
Post ganglionic neuron releases norepinephrine at the target
Target expresses adrenergic receptors aka G-protein coupled receptors
Parasympathetic branch
Post-ganglionic neurons releases Ach onto the target
Target expresses the muscorinic cholinergic receptor (G-protein coupled receptor)
Sympathetic pre ganglion neurons
Originate in thoracic and lumbar regions of spinal cord
Parasympathetic pre ganglion neuron
Originate in sacral region of spinal cord
Cranial nerves
Adrenal medulla
Pre ganglionic sympathetic stimulates
Medulla are modified post ganglionic neurons
Post ganglionic neurons
Release epinephrine directly into blood
Cholinergic receptors
Bind Ach
Nicotinic cholinergic receptor
Ligand-gated Na channels
Muscorinic cholinergic receptor
G-protein coupled
Open Ca and potassium channels
Adrenergic receptors
G-protein coupled
Alpha adrenergic receptors
Most common Bind to NE Cause increase in Ca (smooth muscle contraction) Alpha 1: sympathetic target tissue activates phospholipase C Cause contraction or secretion Alpha 2: GI tract and pancreas Decreases cAMP Cause relaxation (dilate)
Beta 1 adrenergic receptors
Cardiac/kidney
Respond to both NE and epinephrine
Increase in cAMP (intracellular signal)
Beta 2
In locations that lack sympathetic neurons
Respond to epinephrine
Increase cAMP
(Response: dilate vascular smooth muscle)
Beta 3
Adipose tissue
Increase cAMP
Bind to NE over epinephrine
Response: mobilize lipid storage
Properties of a sensory system
- Selective stimulus
- Receptor
- Receptor will convert the stimuli into a voltage change
- If voltage change exceeds threshold an AP is generated
- Afferent neuron delivers AP to the CNS
Chemoreceptors
Taste Olfaction pH Oxygen Glucose
Mechanoreceptors (physical or manual stimuli)
Pressure Bending Tactile Hearing Blood pressure (baro receptors) Equilibrium Lung inflation/deflation Progress through the GI tract Proprioception (position of limbs) Osmolarity (water concentration)
Types of receptors (afferent sensors)
Chemoreceptors (chemical) Mechanoreceptors (physical) Photo receptors (light) Thermal receptors (heat) Nociceptors (pain)
Tonic receptors
Continue to transmit signals as long as stimulus is present
Phasic receptors
Habituate rapidly (cease firing AP if the stimulus is prolonged) Fire AP again when stimulus is removed
Tactile receptors
Skin
Viscera
Mechanosensative cation channels > Na influx > voltage change > initiates AP
Styles of tactile receptors
Free nerve endings (variable responses) Meissner corpuscles (flutter/superficial/adapts rapidly) Parcinion corpuscles (vibration/deeper layers of skin/phasic) Ruffini corpuscles (stretch/deep/tonic) Merkel receptor (steady pressure/superficial/tonic)
Sensory cell v-gated Ca channels
Trp channels (transient receptor potential)
Two types of pain neurons
Fast pain (delta fibers, fast AP) Slow pain (c-fibers, slower AP)
Capsacius
Binds to trp channels
Chemoreceptors
Smell
Taste
Olfaction
Nasal epithelia olfactory receptors
G-protein coupled receptors
Activate (cause an increase in cAMP > cause ion channels to open)
Discrimination between different odorant molecules to the receptors
Lead to hippocampus and amygdala
Olfactory cortex
Smell evokes memory
Taste
Salty Sweet Sour Bitter Umami (savory) All non-spiking neurons
Bitter
Receptor is coupled to a G-protein
PLC
Type 2 taste receptor
PLC
Liberates IP3 IP3 binds to Ca channels on the ER Channel opens Ca into cytoplasm Synaptic vesicle fuse and release NT
Sour
Decrease in pH causes potassium channels to close Activates v-gated Ca channels Ca in Causes vesicles to fuse > release NT Type 3 taste receptor
Salty
Receptor has open Na channels facing surface of tongue
Increase in NaCl in saliva, Na enters the sensor, Na influx causes depolarization
Activate v-gated Ca channels
Ca in
Synaptic vesicles fuse > release NT
Type 1 taste receptor
Sweet
G-protein coupled receptor Activates adenylyl cyclase cAMP causes potassium channel to close Cause depolarization Activate v-gated Ca channels Ca in Synaptic vesicles fuse Release NT Type 2 taste receptor
Hearing
Mechanical receptor
Based on hair cells bending back and forth
Bending because of alternating pressure waves in the air
Pitch
Frequency
How many waves per second
Sounds transduction
- Sound waves
- Mechanical vibrations
- Fluid waves
- Bends the hair cells (mechanical)
- Converted to electrical signals
Hearing 2
Sound waves (pressure) Tympanic membrane vibrates Move the bones of middle ear Push oval window (membrane) Causes waves in the endolymph Organ of Corti Organ of Corti contains hair cells that transform the physical energy of the endolymph waves into electrical energy
Equilibrium
Balance Position of body in space 1. Gravity receptors 2. Proprioceptors 3. Visual
Vision
- Focus light
- Transduce light energy into electrical energy
- Neural processing
Shorter wavelength = more energy
Longer wavelength = less energy
Focusing
Regulates amount of light that reached photoreceptors
Pupils dilate
Decrease in aperture size and increase in depth of field
Lens is rounded (focus on objects close to you)
Ciliary muscles can pull on the lens > flattens (focus on objects farther away)
Photo transduction
Retina
Photo transducer
Synapse with bipolar cells
Synapse with ganglion cells
Axons of ganglion cells are bundled into optic nerve
Fovea > highest concentration of photoreceptors
Rods
Most common
Monochromatic
Very good at low light
Visual pigment rhodopsin
Cones
Concentrated in fovea
High acuity vision
Color vision (discriminate different wavelengths, red, blue, green)
Photoreceptors
Membrane disks
Folded membrane to increase surface area
Transduction mechanism: dark
Photoreceptors have an open Na channel Depolarize Induce Ca influx NT release (glutamate) Increase AP
Transduction mechanism: light
Rhodopsin
>opsin (G-protein coupled receptor)
>retinal (organic carotenoid)
Retina in the dark
Cis-bond Tightly binds to opsin Photon strikes the retinal Absorbs energy Changes structure to trans-bond Can't bind to opsin
Retina in the light
Changes retinal
Frees the opsin receptor
Opsin binds to the G-protein
Activates G-protein
Afferent neurons (somatic motor neurons)
Control skeletal muscle
Muscle
Collection of muscle fibers (muscle cells)
100’s-1000’s of fibers
Each fiber is controlled independently
Myoblast
Myo = muscle
Blast = immature
Form myocytes
Fibers
Attach to connective tissue Bundle fibers together Wrap around outer muscle Protect to the bone Increase strain on muscle > increase amount of connective tissue Protection
Skeletal muscle
Made of many muscle fibers
Wrapped by connective tissue for protection
Myofibrils
Bundles of contractile proteins
Sarcomere
Functional unit of myofibril
Sarcoplasmic reticulum
Modified ER
Wraps around myofibrils
Stores calcium
(Calcium is signal for contraction)