1. Lecture 8. Regulatory Mechanisms
I. Intercellular Communication and the
Endocrine System
II. Nervous Coordination
2. Nervous System
•
detection of external and internal stimuli
•
control and coordination of responses to
stimuli
•
includes the brain, spinal cord, sense organs
3. Neurons: Functional Units of Nervous System
•
sensory or afferent neuron
•
motor or efferent neuron
•
interneuron
6. Neuroglia
also known as glial cells
•
•
non-neuronal cells that
maintain homeostasis,
form myelin, and provide
support and protection for
the brain's neurons
i.e. astocyte,
•
oligodendrocyte and
microglia
7. Astrocyte
biochemical support of endothelial cells that form the
•
blood-brain barrier
•
provision of nutrients to the nervous tissue
•
maintenance of extracellular ion balance
with principal role in the repair and scarring process of the
•
brain and spinal cord following traumatic injuries.
8. Oligodendrocyte
insulation of axons in the central nervous system (the brain
•
and spinal cord) of higher vertebrates
•
provision of nutrients to the nervous tissue
Microglia
the resident macrophages of the brain and spinal cord, and
•
thus act as the first and main form of active immune
defense in the central nervous system
10. Patterns of Organization of Nervous System
• with cephalization come more complex
nervous systems
11. Nature of Nerve Signals
•
every cell has a voltage or membrane potential
across its plasma membranes
•
a membrane potential is a localized electrical
gradient across membrane
–
anions are more concentrated within a cell
–
cations are more concentrated in the extracellular
fluid
12. •
Measuring Membrane Potentials
•
an unstimulated cell usually has a resting potential of -70mV
13. •
How a Cell Maintains a Membrane Potential
–
Cations
• K+ the principal intracellular cation
• Na+ is the principal extracellular cation
–
Anions
• proteins, amino acids, sulfate, and phosphate are the
principal intracellular anions
• Cl– is principal extracellular anion
14. •
Ungated ion channels allow ions to diffuse
across the plasma membrane
–
these channels are always open
•
this diffusion does not achieve an equilibrium
since Na-K pump transports these ions against
their concentration gradients
15. •
changes in membrane potential of a neuron give
rise to nerve impulses
•
excitable cells have the ability to generate large
changes in their membrane potentials
–
gated ion channels open or close in response to
stimuli
• the subsequent diffusion of ions leads to a change in the
membrane potential
16. •
Types of gated ions:
–
chemically-gated ion channels open or close in
response to a chemical stimulus
–
voltage-gated ion channels open or close in response
to a change in membrane potential
17. •
Graded Potentials: Hyperpolarization and
Depolarization
–
graded potentials are changes in membrane
potential
20. •
The Action Potential:
All or Nothing
Depolarization
–
if graded potentials sum
to -55mV a threshold
potential is achieved
• triggers an action
potential
–
Axons only
21. •
In the resting state closed voltage-gated K+
channels open slowly in response to
depolarization
•
Voltage-gated Na+ channels have two gates
–
closed activation gates open rapidly in response to
depolarization
–
open inactivation gates close slowly in response to
depolarization
22.
23. • nerve impulses
propagate themselves
along an axon
• the action potential is
repeatedly regenerated
along the length of the
axon
24. •
Saltatory conduction
–
in myelinated neurons only unmyelinated regions of
the axon depolarize
• thus, the impulse moves faster than in unmyelinated
neurons
25.
26. •
Electrical Synapses
–
action potential travels directly from the presynaptic
to the postsynaptic cells via gap junctions
• Chemical Synapses
– more common than electrical synapses
– postsynaptic chemically-gated channels exist for ions
such as Na+, K+, and Cl-
• depending on which gates open the postsynaptic neuron
can depolarize or hyperpolarize
27.
28. Neurotransmitters
•
Acetylcholine
–
excitatory to skeletal muscle
–
inhibitory to cardiac muscle
–
secreted by the CNS, PNS, and at vertebrate
neuromuscular junctions
29. •
Biogenic Amines
–
Epinephrine and norepinephrine
• can have excitatory or inhibitory effects
• secreted by the CNS and PNS
• secreted by the adrenal glands
epinephrine norepinephrine
30. •
Dopamine
–
generally excitatory; may be inhibitory at some
sites
• widespread in the brain
• affects sleep, mood, attention, and learning
–
secreted by the CNS and PNS
–
a lack of dopamine in the brain is associated with
Parkinson’s disease
–
excessive dopamine is linked to schizophrenia
31. Parkinson’s disease
•
degenerative disorder of the central nervous system that
often impairs the sufferer's motor skills, speech, and other
functions
•
characterized by muscle rigidity, tremor, postural
abnormalities, gait abnormalities, a slowing of physical
movement (bradykinesia) and a loss of physical movement
(akinesia) in extreme cases
32. Schizoprenia
mental disorder characterized by a disintegration of the
•
process of thinking and of emotional responsiveness
auditory hallucinations, paranoid or bizarre delusions, or
•
disorganized speech and thinking, and it is accompanied by
significant social or occupational dysfunction
33. •
Serotonin
–
generally inhibitory
• widespread in the brain
• affects sleep, mood, attention, and learning
–
secreted by the CNS
34. •
Amino Acids
–
Gamma aminobutyric acid (GABA)
• inhibitory
• secreted by the CNS and at invertebrate
neuromuscular junctions
–
Glycine
• inhibitory
• secreted by the CNS
35. •
Amino Acids
–
Glutamate
• excitatory
• secreted by the CNS and at invertebrate
neuromuscular junctions
–
Aspartate
• excitatory
• secreted by the CNS
36. •
Neuropeptides
–
Substance P
• excitatory
• secreted by the CNS and PNS
–
Met-enkephalin (an endorphin)
• generally inhibitory
• secreted by the CNS
37. •
Gases that act as local regulators
–
Nitric oxide
–
Carbon monoxide
41. •
A ganglion is a cluster of nerve cell bodies
within the peripheral nervous system.
•
A nucleus is a cluster of nerve cell bodies
within the central nervous system.
45. • Brain and spinal cord
– central canal is continuous with ventricles;
contain cerebrospinal fluid (CSF)
– white matter is composed of bundles of
myelinated axons
– gray matter consists of unmyelinated axons,
nuclei, and dendrites
46.
47.
48. •
A Simple Nerve Circuit – the Reflex Arc in Vertebrates
–
A reflex is an autonomic response
55. – functions in homeostasis, coordination of movement,
conduction of impulses to higher brain centers
– relays information to and from higher brain centers
56. •
Midbrain
–
contains nuclei involved in the integration of
sensory information
• superior colliculi are involved in the regulation
of visual reflexes
• inferior colliculi are involved in the regulation of
auditory reflexes
57. •
Medulla oblongata
–
contains nuclei that control visceral (autonomic
homeostatic) functions
–
breathing
–
heartbeat and blood pressure
–
swallowing
–
vomiting
digestion
• Pons
–
– contains nuclei involved in the regulation of
visceral activities such as breathing
58. Cerebellum
• functions for coordination of motor activities, and
perceptual and cognitive factors
• relays sensory information about joints, muscles, sight, and
sound to the cerebrum.
• coordinates motor commands issued by the cerebrum
60. thalamus
• relays all sensory information to the cerebrum
• relays motor information from the cerebrum
• receives input from the cerebrum
• receives input from brain centers involved in the regulation
of emotion and arousal
61. hypothalamus
• regulates autonomic activity
– contains nuclei involved in thermoregulation, hunger,
thirst, and sexual and mating behavior
– regulates the pituitary gland
• in mammals, the hypothalamic suprachiasmatic nuclei
(SCN) function as a biological clock
63. • association areas (where sensory
information is integrated and assessed and
motor responses are planned)
64. (memory, (sensory
emotion, reception and
planning, integration;
judgement and taste)
aggression)
(learning, memory,
hearing, smell, visual
recognition, emotional
behavior)
65.
66. •
Lateralization of Brain Function
–
The left hemisphere
• specializes in language, math, logic operations, and
the processing of serial sequences of information,
and visual and auditory details
• specializes in detailed activities required for motor
control
–
The right hemisphere
• specializes in pattern recognition, spatial
relationships, nonverbal ideation, emotional
processing, and the parallel processing of
information
67. •
Language and Speech
–
Broca’s area
• usually located in the left hemisphere’s frontal lobe
• responsible for speech production
–
Wernicke’s area
• usually located in the right hemisphere’s temporal lobe
• responsible for the comprehension of speech
–
Other speech areas are involved in generating
verbs to match nouns, grouping together related
words, etc
68. The Limbic System
- hippocampus
- olfactory cortex
- inner portions of the cortex’s lobes
- parts of the thalamus and hypothalamus
69. The Limbic System
• mediates basic emotions (fear, anger), involved in
emotional bonding, establishes emotional memory
– e.g., the amygdala is involved in recognizing the
emotional content of facial expression
70. •
Memory and Learning
–
short-term memory stored in the frontal lobes
–
establishment of long-term memory involves the
hippocampus
71. • The transfer of information from short-term to
long-term memory
– enhanced by repetition
– influenced by emotional states mediated by the
amygdala
– Influenced by association with previously stored
information.
72. Cranial Nerves
•
nerves that emerge directly from the brain
•
In humans, there are 12 pairs of cranial nerves
•
1st and 2nd pair – cerebrum
•
3rd – 12th pair – brainstem
74. Cranial Nerves
Cranial Nerve Type
I. Olfactory Sensory
II. Optic Sensory
III. Occulomotor Motor
IV. Trochlear Motor
V. Trigeminal Both
VI. Abducent Motor
VII. Facial Both
VIII. Auditory Sensory
IX. Glossopharyngeal Both
X. Vagus Both
XI. Accessory Motor
XII. Hypoglossal Motor
75. Sensory Systems
• sensations begin as different forms of energy
that are detected by sensory receptors
– energy is converted to action potentials that
travel to appropriate regions of the brain
76. •
Sensations are action potentials that reach the
brain via sensory neurons.
•
Perception is the awareness and interpretation
of the sensation.
77. •
Sensory reception begins with the detection of
stimulus energy by sensory receptors.
–
Exteroreceptors detect stimuli originating outside
the body.
–
Interoreceptors detect stimuli originating inside the
body.
–
Sensory receptors convey the energy of stimuli into
membrane potentials and transmit signals to the
nervous system.
• involves sensory transduction, amplification,
transmission, and integration.
78. •
Sensory Transduction
–
conversion of stimulus energy into a change in
membrane potential
–
Receptor potential: a sensory receptor’s version of
a graded potential
79. •
Amplification
–
the strengthening of stimulus energy that can be
detected by the nervous system
80. •
Transmission
–
the conduction of sensory impulses to the CNS
–
some sensory receptors must transmit chemical
signals to sensory neurons
• the strength of the stimulus and receptor potential
affects the amount of neurotransmitter released by the
sensory receptor
–
some sensory receptors are sensory neurons
• the intensity of the receptor potential affects the
frequency of action potentials
81. •
Integration
–
the processing of sensory information.
• begins at the sensory receptor
–
sensory adaptation is a decrease in
responsiveness to continued stimulation
–
the sensitivity of a receptor to a stimulus will
vary with environmental conditions
83. •
Mechanoreceptors respond to mechanical
energy.
–
muscle spindle is an interoreceptor that responds
to the stretching of skeletal muscle.
–
hair cells detect motion
Pacinian corpuscle –
mechanoreceptor in
the skin that detects
pressure and
vibration
84. •
Pain receptors = nocioceptors
–
different types of pain receptors respond to
different types of pain
–
Prostaglandins increase pain by decreasing a pain
receptor’s threshold
85. •
Thermoreceptors respond to heat or cold
–
respond to both surface and body core
temperature
86. •
Chemoreceptors respond to chemical stimuli.
–
general chemoreceptors transmit information
about total solute concentration
–
specific chemoreceptors respond to specific types
of molecules
–
internal chemoreceptors respond to glucose, O2,
CO2, amino acids, etc.
–
external chemoreceptors are gustatory receptors
and olfactory receptors
87. •
Electromagnetic receptors respond to
electromagnetic energy
–
Photoreceptors respond to the radiation we know
as visible light
–
Electroreceptors: some fish use electric currents to
locate objects
88. Photoreceptors and Vision
• Eye cups are among the simplest
photoreceptors
– detect light intensity and direction — no image
formation
– the movement
of a planarian is
integrated with
photoreception
89. •
Image-forming eyes
–
compound eyes of insects and crustaceans.
• Each eye consists
of ommatidia,
each with its own
light-focusing lens.
90. •
Single-lens eyes of invertebrates such as jellies,
polychaetes, spiders, and mollusks
–
the eye of an octopus works much like a camera
and is similar to the vertebrate eye
92. •
Accommodation is the focusing of light in the
retina.
–
In squid, octopuses, and many fish this is
accomplished by moving the lens forward and
backward.
93. –
In mammals, accommodation is accomplished by
changing the shape of the lens
94. •
Photoreceptors of the human retina
–
About 125 million rod cells
–
About 6 million cone cells
95. •
Rhodopsin (retinal + opsin) is the visual pigment of
rods.
•
The absorption of light by rhodopsin initiates a signal-
transduction pathway.
96. • Visual processing begins with
rods and cones synapsing with
bipolar cells
– Bipolar cells synapse with
ganglion cells
• Visual processing in the retina
also involves horizontal cells
and amacrine cells
98. •
Lateral pathways:
–
Photoreceptors horizontal cells other
photoreceptors.
• Results in lateral inhibition.
–
More distance photoreceptors and bipolar
cells are inhibited sharpens edges and
enhances contrast in the image.
–
Photoreceptors bipolar cells amacrine cells
ganglion cells.
• Also results in lateral inhibition, this time of the
ganglion cells.
99. •
The optic nerves of the two
eyes meet at the optic chiasm.
–
Where the nasal half of each
tract crosses to the opposite side.
•
Ganglion cell axons
make up the optic tract.
–
Most synapse in the
lateral geniculate
nuclei of the thalamus.
• Neurons then convey
information to the
primary visual cortex
of the optic lobe.
102. •
Vibrations in the cochlear fluid basilar
membrane vibrates hair cells brush against
the tectorial membrane generation of an
action potential in a sensory neuron.
103.
104. •
Pitch is based on the location of the hair cells
that depolarize.
•
Volume is determined by the amplitude of the
sound wave.
105. • the inner ear also contains the organs of equilibrium
106.
107. •
Statocysts are mechanoreceptors that function in
an invertebrate’s sense of equilibrium.
108. •
sound sensitivity in insects depends on body
hairs that vibrate in response to sound waves
–
different hairs respond to different frequencies
•
many insects have a
tympanic membrane
stretched over a
hollow chamber
110. •
In mammals, taste receptors are located in taste
buds, most of which are on the surface of the
tongue.
•
Each taste receptor responds to a wide array of
chemicals.
111. •
Sensory receptors transduce stimulus energy and transmit signals
to the nervous system
112. •
In mammals, olfactory receptors line the upper
portion of the nasal cavity
–
the binding of odor molecules to olfactory receptors
initiate signal transduction pathways
