Chapter 3 Flashcards
Na/k ATPase action
3 Na ions out, 2 K ions in with the hydrolysis of one ATP molecules through primary active transport
Resting membrane potential of neurons
-70mV
Voltage-gated sodium channels: activation threshold potential
-50mV
Neuron depolarization goes to what voltage
~+35mV
All-or-nothing response
All channels will open fully if the depolarization hits the threshold
Voltage-gated K channels compared to voltage-gated Na channels
Voltage-gated Na channels depolarize membrane where K channels open and repolarize the membrane
* K channels are slower to open but remain open for longer than Na channels
Axons of many neurons are wrapped in _____ created by ____
insulating myelin sheath
Schwann cells (type of glial cell)
Schwann cells
One of the two peripheral nervous system supporting (glial) cells. Schwann cells form the myelin sheath on axons of peripheral neurons
Nodes of Ranvier
where the channels are concentrated because there are no membrane depolarization and no voltage-gated sodium channels where the myelin is
Saltatory conduction
rapid jumping of action potentials between nodes
o Speeds up movement of APs
Types of effectors
muscles and glands
Central nervous system
- Spinal cord
- Hindbrain:
- Midbrain:
- Forebrain:
Hindbrain
Medulla
Pons:
Cerebellum:
Midbrain
relay for visual and auditory information and contains much of the reticular activating system (RAS) which is responsible for arousal or wakefulness
Forebrain
includes the diencephalon and telencephalon:
Diencephalon
thalamus and hypothalamus
thalamus
relay and processing centre for sensory info
hypothalamus
interacts directly with many parts of the brain. Contains centres for controlling emotions and autonomic functions
o Plays major role in hormone production and release
o Primary link between nervous and endocrine system
Telencephalon
cerebral hemispheres, corpus callosum, cerebrum
cerebrum
largest region of the human brain (encompasses the cerebral hemispheres)
o Cerebral cortex: outer layer of grey matter
Grey matter consists of somas and white matter consists of myelinated axons
Cerebral hemispheres (and their lobes)
generally, most people tend to be left brain dominant. Left hemisphere is responsible for speech and right hemisphere is responsible for visual-spatial reasoning and music
o Responsible for conscious thought processing and intellectual functions
o Play a role in processing somatic sensory and motor information
Composed of lobes:
Frontal lobe:
Parietal lobes:
Temporal lobes:
Occipital lobes:
Wernicke’s area
language comprehension
Broca’s area
language production
frontal lobe
initiates voluntary movement and involved in complex reasoning skills and problem solving
Parietal lobes
involved in general sensation (touch, temp, pressure, vibration, etc) and gustation (taste)
Temporal lobes
process auditory and olfactory sensation and involved in short-term memory, language comprehension, and emotion
Occipital lobes
process visual sensation
Basal nuclei (cerebral nuclei, basal ganglia)
gray matter deep within cerebral hemispheres. Broadly function in voluntary motor control and procedural learning related to habits
Works with cerebellum to process and coordinate movement initiated by the primary motor cortex
* Basal nuclei is inhibitory and cerebellum is excitatory
Limbic system
located between cerebrum and diencephalon. Includes: amygdala, cingulate gyrus, hippocampus.
Important for emotion and memory
Brainstem
medulla, pons, and midbrain
Quick summary of roles:
1. Spinal cord
2. Medulla
3. Pons
4. Cerebellum
5. Midbrain
6. Thalamus
7. Hypothalamus behaviour
8. Basal nuclei
9. Limbic system
10. Cerebral cortex
11. Corpus collosum
Quick summary:
1. Spinal cord –> simple reflexes
2. Medulla –> involuntary functions
3. Pons –> relay station and balance
4. Cerebellum –> movement coordination
5. Midbrain –> eye movement
6. Thalamus –> integrating center and relay station
7. Hypothalamus –> homeostasis and behaviour
8. Basal nuclei –> movement (inhibitory)
9. Limbic system –> emotion, memory, learning
10. Cerebral cortex–> perception, skeletal muscle movement, memory, attention, thought, language, and consciousness
11. Corpus collosum –> connection between hemispheres
Peripheral nervous system Anatomical Organization (think nerves)
All neurons entering and exiting the CNS are carried by 12 pairs of cranial nerves and 31 pairs of spinal nerves
Cranial nerves (one example)
covey sensory and motor information to and from brainstem
E.g., vagus nerve: acts on heart and GI tract to increase HR and decrease GI activity
* Part of the parasympathetic division of ANS
* Axons of the vagus nerve are preganglionic and end in ganglia which synapse to postganglionic neurons on surface of heart, stomach, and other visceral organs.
Spinal nerves
convey sensory and motor information to and from spinal cord
Somatic PNS anatomy: what do they innervate, what neurotransmitter do they use, what are their dendrites like?
o All somatic motor neurons innervate skeletal muscle cells, use Ach as their neurotransmitter and have cell bodies in the brain stem or ventral (front) spinal cord
o All somatic sensory neurons have a long dendrite extending from sensory receptors towards the soma (located just outside the CNS) in a dorsal root ganglion (spinal cord)
Dorsal root ganglion
a bunch of somatic (and autonomic) sensory neuron cell bodies located just dorsal (back) of the spinal cord
* There is a dorsal root ganglion for every segment of the spinal cord
* They are protected by vertebral column but are outside meninges (therefore outside the CNS)
preganglionic neuron
one of two efferents of the sympathetic and parasympathetic systems
Preganglionic neuron: has its cell body in brainstem or spinal cord and sends axon to an autonomic ganglion outside the spinal cor
sympathetic system (thoraco-lumbar system) efferent neurons
All sympathetic system (thoraco-lumbar system) has its preganglionic efferent neurons cell bodies in the thoracic or lumbar spinal cord
General function: fight or flight, mobilize energy
Preganglionic axon is relatively short, release ACh
Only a few ganglia which are quite large, close to the cord and far from target
Postganaglionic cells send a long axon to the effector (norephinephrine)
Parasympathetic system (craniosacral system) efferent neurons
Parasympathetic system (craniosacral system) has all its preganglionic neuron cell bodies in the brainstem or n the sacral portion
General function: rest and digest, store energy
Preganglionic neurons send a long axon (ACh)
Small ganglion, far from cord, close to targe
Postganglionic cells are close to the effector and release ACh
postganglionic cell
Postsynaptic neuron: synapses with the ganglion and sends an axon to an effector (smooth muscle of glad)
All autonomic preganglionic neurons release _____ as their neurotransmitter
acetylcholine
All parasympathetic postganglionic neurons release _____ as their neurotransmitter
acetylcholine
Nearly all sympathetic postganglionic neurons release _______
norepinephrine
Autonomic afferent (sensory) neurons similarity and difference to somatic afferent neurons
similar to somatic afferent neurons with one exception:
o they can synapse in the PNS (at autonomic ganglia) with autonomic efferent neurons in a “short reflex”
Adrenal medulla part of what nervous system?
Part of the sympathetic nervous system
o Embryologically derived from sympathetic postganglionic neurons and directly innervated by sympathetic preganglionic neurons
Inner and outer portions of adrenal medulla
- Inner portion of adrenal is medulla and the outer portion is the cortex
Adrenal medulla cortex is an important ______
endocrine gland
Adrenal medulla cortex secretes ____
Secretes glucocorticoids (e.g., cortisol), mineralocorticoids (e.g., aldosterone) and some sex hormones
With the activation of the sympathetic system, the adrenal gland releases____
epinephrine/adrenaline
o Epinephrin is a hormone b/c it is released into the bloodstream by a ductless gland
Acts very fast and effects are short-lived
Medulla
relay centre. Regulates vital autonomic functions (blood pressure, digestive function, respiration)
Pons
connection between brain stem and cerebellum. Controls some autonomic functions and coordinates movement – plays a role in balance and antigravity posture (receives info from vestibular system)
Cerebellum
complex movement coordination. Involved in balance (receives info from vestibular system)
Exteroceptors
sensory receptors that detect stims from the outside world
Interoceptors
detect internal stims
Types of sensory receptors (and examples)
Mechanoreceptors: respond to mechanical disturbances
Pacinian corpuscles: pressure sensors deep in skin (looks like an onion)
Auditory hair cells: vibrates with wave sounds
Vestibular hair cells: in the semicircular cannels and inner ear – detect acceleration and position relative to gravity
Autonomic mechanoreceptor example would be one that detects stretch in intestinal wall
Chemoreceptors: respond to particular chemicals
Olfactory receptors
Gustatory receptors
Autonomic mechanoreceptor in walls of carotid and aortic arteries respond to changes in arterial pH, PCO2 and PO2 levels
Nociceptors: pain receptors
simplest type of sensory receptor, generally consisting of free nerve endings that detects chemical signals of tissue damage (sorta like a simple chemoreceptor)
May be somatic or autonomic (Autonomic pain receptors frequently give a dull aching pain –> May give illusion of pain on the skin when their nerves cross paths with skin somatic afferents (referred pain)
Thermoreceptors: stimulated by changes in temperature
Autonomic and somatic examples
Peripheral thermoreceptors: cold-sensitive, warm-sensitive, and thermal nociceptors (painfully hot)
Electromagnetic receptors: stimulated by electromagnetic waves
Photoreceptors are the only human examples (rods and cones)
Receptor activation results in nerve endings being depolarized and signals sent up dendrite in what type of potential?
grade potential (not action potential)
4 properties of stimulus
modality, location, intensity, duration
Tonic receptors
fire action potentials as long as the stim continues
* Subject to adaptation and frequency of AP decreases as the stim continues at the same level
Phasic receptors
only fire Aps when the stim begins and do not explicitly communicate duration
* Important for changes in stim and essentially adapt immediately
Proprioceptor examples
broad category of many different types of receptors including:
o E.g., muscle spindle: a sensory organ specialized to detect muscle stretch (mechanoreceptor)
o E.g., Golgi tendom organs: monitor tension in tendons
o E.g., Joint capsule receptors: detect pressure, tension and movement of joints
Proprioception
Proprioception: awareness of self (ie. Body position) –> kinesthetic sense
Olfactory nerves project directly to _____ of the brain located in the _____ lobe near the ______ (important for emotion and memory)
olfactory bulbs
temporal
limbic system
Organ of corti
basilar membranes, hair cells, and tectorial membrane
o Organ of corti and cochlea are primary site that auditory stimuli are detected
Summary: from sound to hearing
Sound waves –> auricle/pinna –> external auditory canal –> tympanic membrane –> malleus –> incus –> stapes –> oval window –> perilymph –> endolymph –> basilar membrane –> auditory hair cells –> tectorial membrane –> NTs stimulate bipolar auditory neurons –> brain –> perception
Vestibular complex: what is it composed of, what motion does it detect, what is it innervated with, where do the neurons project to?
Vestibular complex made of 3 semicircular canals: utricle, saccule, and ampullae
All tubes filled with endolymph and hair cells that detect motion (rotational accelerations of the head)
* static equilibrium
* linear acceleration
Innervated by afferent neurons which send balance info to the pons, cerebellum, and other areas
Macula
: special centre region of the retina the processes what is directly infront
Fovea centralis
(focal point): centre of macula which contains only cones and is responsible for extreme visual acuity
Photoreceptors
contain special pigment proteins (opsins) that change their tertiary structure upon absorbing light.
o Each opsin is bound to one molecule and contains one molecule of retinal (derived from Vit A)
o In the dark, retinal has several trans double bonds and one cis double bond
In this formation, retinal and opsin keep the sodium channel open and the cell remains repolarized
o In light, a photon is absorbed, retinal is converted to the all-trans form which triggers a series of reactions that ultimately closes the Na channel and the cell hyperpolarizes!
Rods and cones synapse on _____ which then synapses on ____
bipolar cells
Bipolar cell synapses onto the ganglion cell (whose axons form optic nerve) which causes depolarization and an AP travels along the axon of the ganglion cell to the brain
Rods and cones action in the dark
During their depolarization in the dark, they release NT glutamate onto the bipolar cells, inhibiting them
Rods and cones action in the light
Once absorbing a photon and subsequent hyperpolarization, the photoreceptor stops releasing glutamate and the bipolar cell can depolarize
Rods
responsible for night vision. More sensitive to dim light and motion, more concentrated in their periphery of the retina
Cones
require an abundance of light and also responsible for color vision and high-acuity visions (concentrated in fovea!)
o Color vision depends of presence of 3 types of cones: blue, green, and red absorbing cones
o Brain perceives hues by integrating the relative input of these basic stims
Emmetropia
normal vision
Myopia
nearsightedness. Too much refraction at the lens or an abnormally long eyeball results in a focal length that is too short
o Corrected by a concave (diverging) lens
Hyperopia
farsightedness. Too little refraction at lens or abnormally short eyeball results in a focal length that is too long
o Corrected by a convex (converging) lens
Presbyopia
inability to accommodate (focus) due to loss of flexibility in lens
o Occurs with aging
Feature-detection theory
a theory of visual perception that proposes certain neurons fire for individual and specific features of a visual stimulus, such as shape, color, lines, movement, etc
Parallel processing
a system whereby many aspects of a stimulus are processed simultaneously instead of in a step-by-step or serial manner
Retinal disparity
a binocular cue whereby the brain compares images from each retina to perceive distance
o Greater disparity = closer object
Convergence
anther binocular cue describing the extent the eyes turn inward
o greater convergence strain = closer object
Monocular cues
Information dependent on either eye alone. Important for judging distances of far objects (small retinal disparity)
o Relative size
o Interposition: if one object is in front of another
o Relative clarity
o Texture gradient
o Relative height: objects higher in the visual field look further away
o Relative motion: objects closer move faster
o Linear perspective: parallel lines appear to converge
o Light and shadow: closer objects reflect more light than distant ones
Absolute threshold
minimum stim intensity required to activate sensory receptor 50% of the time
Difference thresholds
just notice-able difference ; the minimum noticeable difference b/w two stims
Weber’s law
two stimuli must differ by a constant proportion in order for their differences to be perceptible
Weight for humans must differ by 2%
Light intensity by 8%
Tone frequency by 0.3%
Signal detection theory
detecting sensory stims depends on the info itself, but also on our psychological state (alertness, expectation, motivation, and prior experience)
o Four possible outcomes: hit, miss, false alarm, correct rejection
Gestalt Psychology
an organized whole is perceived as more than the sum of its individual parts (e.g., a face, not a collection of nose, eyes, ears, etc)
Emergence (visual system)
when attempting to identify an object, we first identify its outline, which then allows us to figure out what the object is. Once the whole emerges do we start to identify the parts of the whole
E.g., a photo of a dog is first a dog and then face, legs, leash, etc.
Figure/ground
we have a perceptual tendency to separate figure or objects from everything else (background) based on many variables (like size, shadow, contrast, color, position, etc)
E.g., vase – face optical illusion
Multistability
tendency of ambiguous images to pop back and forth unstably between alternative interpretations of our brain (isn’t explaining how)
Gestalt laws of grouping
tend to perceive things as connected in arbitrary ways
Law of proximity (grid of dots), low of continuity (Ven diagram), law of closure (invisible shape), law of common fate (birds flying), law of connectedness (box around part of a grid)
Perceptual processing types
brains use a combination of bottom-up and top-down sensory processing
Nervous system communicates with ____ and endocrine system communicates with _____
Action potentials
Hormones
Endocrine system
takes longer than nervous system to act but generally has a longer effect
o Regulates physiology for periods of hours to days
o Interconnected with nervous system as neurons can signal release of hormones from endocrine glands (e.g., adrenal medulla)
HPA axis is a primary connection between the two systems
Endocrine gland
a ductless gland whose secretory products are picked up by capillaries supplying blood to the region
Exocrine glands
secrete products into external environment (gastrointestinal lumen or external world) with ducts
Hormone receptor
polypeptide with a ligand-specific binding site. Binding of hormone causes receptor to modify target cell activity
Autocrine activity
some signalling molecules modify the activity of the cell that secreted them
o e.g., T cell secretes interleukin 2 which binds to receptors on the same T cell to stimulate increased activity
Hormone
a molecule secreted into bloodstream by endocrine gland and has its effect on distant target cells with the right receptor
Hydrophilic hormones
must bind to receptors on cell surface
Peptide hormones
Cannot cross biological membranes (hydrophilic) so must communicate with interior of target cell with second messenger cascade
Peptide binds to polypeptide receptor -> catalytically activate second messenger -> function of proteins in cytoplasm changed
Allows amplification as a few receptors change activity of many enzymes in cytoplasm
Because peptides modify activity of existing enzymes in cytoplasm, their effects are rapid (minutes to hours) and generally short-lived
Polypeptide: complex structure proteins (e.g., insulin)
Amino-acid derivatives: single amino acid and contains no peptide bonds (e.g., catecholamines -> epinephrine)
- Hydrophobic hormones
bind to receptors in cellular interior Steroid hormones
o Cannot dissolve in plasma so moves through bloodstream on (hydrophobic interaction) proteins in plasma
o Can diffuse through plasma membrane to bind to a receptor in the cytoplasm ->Once it has bound its ligand, the steroid hormone-receptor complex is transported into the nucleus where it acts as a sequence-specific regulator of transcription
o Because steroids must modify transcription to change the amount and/or type of proteins in the cell, their effects are exerted slowly, over a period of days and persist for days to weeks
o Steroids regulating sexuality, reproduction and development are secreted by the testes, ovaries and centra
o Steroids regulating water balance and other processes are secreted by adrenal cortex
o All other endocrine glands secrete peptide hormones
Regulation of endocrine system is not _____ or ____ structure, it is generally ____
Regulation of endocrine system is not preplanned or rigidly structure, it is generally autonomic
How is the endocrine system controlled?
o Hormone levels rise and fall based on physiological needs with feedback systems
o Many of the functions of the endocrine system depend on instructions from the hypothalamus -> it releases tropic hormones that regulate other topic hormones called releasing and inhibiting factor/hormones (e.g., HPA axis)
Tropic hormone
a hormone that controls the release of another hormone
Negative feedback/feedback inhibition
a biological process that works by maintaining stability or homeostasis; a system produces a result which feeds back to stop the system and maintain the result within tightly controlled bounds
Hypothalamic-pituitary control axis
Hypothalamus controls the anterior pituitary which controls most of the endocrine system
Damage to the H-P connection is fatal unless hormone replacement therapy is given
Hypothalamic-pituitary portal system: a unique, simple miniature circulatory system for efficient transport for hypothalamic releasing and inhibiting factors to the anterior pituitary
It is a portal system because there are two capillary beds in sequence allowing for direct communication between nearby structures
Hypophysis
another name for pituitary gland
Anterior pituitary (adenohypophysis)
made of glandular tissue. The anterior pituitary is controlled by releasing and inhibiting factors (essentially trophic factors) from the hypothalamus
o It is a normal endocrine gland
o It makes and secretes 6 different hormones: FSH, LH, ACTH, TSH, prolactin and growth hormone.
Posterior pituitary (neurohypophysis)
made or nervous tissue (neurons). The posterior pituitary is controlled by APs from the hypothalamus
o The hypothalamic neurons that send axons down to the posterior pituitary are examples of neuroendocrine cells (neurons that secrete hormones into the bloodstream)
o Stores and secretes two hormones made by the hypothalamus: oxytocin and ADH (antidiuretic hormone or vasopressin).
Thyroid hormones
produced from the amino acid tyrosine in the thyroid gland and has broad effects on metabolism and energy usage
Production of thyroid hormone is increased by thyroid stimulating hormone (TSH) from anterior pituitary in turn regulated by hypothalamus and CNS)
Mechanism of action is to bind to a receptor in the cytoplasm of cells that then regulates transcription in the nucleus
Effect of this regulation is to increase the overall metabolic rate and body temperature (and in children to stimulate growth)
Exposure to cold can increase production of thyroid hormone
Cortisol
secreted in adrenal cortex in response to ACTH from pituitary
In general, cortisol helps body deal with stress but mobilizing glycogen and fat stores to provide energy during stress and increase consumption of proteins for energy
Removal of adrenal cortex can result in death of animals exposed to even small stress
Selective attention (and how it is demonstrated)
process by which one input is attended to and the rest are tuned out
o Demonstrated in study with dichotic listening. Attended channel is the input participants are told to listen to and unattended channel they are told to ignore
They will remember the attended channel info not the unattended
Same observation seen with visual stimuli
Resource model
suggests we have limited capacity to pay attention so must devote resources carefully
