Title: Nervous Systems
1Nervous Systems
2Nervous Systems
3Evolution of the Nervous System
- Nerve Net
- Cnidarian, Ctenophora
- Nerve Ring with radial nerves
- Echinodermata
- Bilateral Nervous Systems
- Cephalization (ganglia or brain)
- Nerve cord
4Evolution of the Nervous System
- Bilateral Nervous Systems
- Ganglia and two or more longitudinal nerve cords
- platyhelminthes, some mollusca
- Ganglia (brain) and ventral nerve cord
- annelida, arthropoda, some mollusca
- Brain and dorsal nerve cord
- chordata
5Overview of a Nervous System
6Overview of a Nervous System
- Sensory Input
- conduction of signals from sensory receptors
- PNS
- Integration
- environmental information is interpreted
- CNS (brain and spinal cord)
- Motor Output
- conduction of signals to effector cells
- PNS
7Neurons
8Neurons
- Cell body
- nucleus and organelles
- Dendrites
- short and branched
- toward cell body
- Axons
- long and unbranched
- away from cell body
9Axons
- Myelin Sheath - insulating layer
- Node of Ranvier - gaps between Schwann Cells
- Synaptic Terminals - neuron ending
10Clusters of Neurons
- Ganglion
- Cluster of nerve cell bodies in the PNS
- Nuclei
- Cluster of cells in the brain
11Supporting Cells
- Glia (glue)
- Astrocytes (structural support)
- Creates tight junctions and forms the blood-brain
barrier - Radial Glia
- Form tracks for new neurons formed in the neural
tube - Oligodendrocytes
- Form myelin sheath in brain
- Schwann Cells
- Form myelin sheath in the PNS
12Reflex
- Sensory neuron to a motor neuron
13Neural Signals
- Membrane Potential
- Sodium-Potassium Pump
14Threshold Potential
15Resting State
- Both sodium and potassium activation gates are
closed - Interior of cell is negative
16Depolarization State
- Sodium activation gates are opened on some
channels - Interior of cell becomes more positive
17Rising Phase of Action Potential
- Most sodium activation gates are opened
- Potassium activation gates are still closed
18Falling Phase of Action Potential
- Inactivation gates on sodium channels are closing
- Activation gates on potassium channels are opened
- interior of cell becomes more negative
19Undershoot
- Both gates to sodium channels are closed
- Potassium channels are closing
- Membrane returns to its resting state
20Propagation of the Action Potential
- Localized event
- First action potentials depolarization sets off
second action potential - Travels in one direction due to refractory period
21Salatory Conduction
- Action Potential jumps from node to node
- Speeds up signal from 5 m/sec to 150 m/sec
22Communication Between Synapses
- Electrical Synapses
- gap junctions allow for direct transfer of action
potential (used during escape responses) - Chemical Synapses
- uses neurotransmitters
23Chemical Synapse
24Chemical Synapses
- Action potential triggers an influx of calcium
- Synaptic vesicles fuse with presynaptic membrane
- Neurotransmitter released into synaptic cleft
- Neurotransmitters bind to receptors and open ion
channels on postsynaptic membrane which sets off
new action potential - Neurotransmitters are degraded by enzymes or
removed by a synaptic terminal
25Neurotransmitters
26Postsynaptic Potentials
27Postsynaptic Potentials
- Subthreshold
- doesnt reach threshold
- Temporal Summation
- two signals do not reach threshold level but
occur close enough to set off action potential - Spatial Summation
- two signals are set off at the same time setting
off an action potential - Spatial Summation with an inhibitor
- doesnt reach threshold
28Vertebrate Nervous System
29Central Nervous System
- Ventricles (4)
- Cerebrospinal fluid
- White Matter
- Made up of axons
- Gray Matter
- Made up of dendrites
30Peripheral Nervous System
31Peripheral Nervous System
- Autonomic Nervous System regulates the internal
environment (usually involuntary) - Somatic Nervous System regulates the external
environment (usually voluntary)
32Autonomic Nervous System
33Autonomic Nervous System
- Sympathetic Division
- Flight or fight response
- Parasympathetic Division
- Rest or digest response
34Brain
35The Brainstem
- The Medulla Oblongata and the Pons controls
breathing, heart rate, digestion - The Cerebellum controls coordination of movement
and balance
36The Midbrain
- The Midbrain receives, integrates, and projects
sensory information to the forebrain
37The Diencepholon
- Forebrain
- Epithalamus
- Includes the pineal gland and the choroid plexus
- Thalamus
- conducts information to specific areas of
cerebrum - Hypothalamus
- produces hormones and regulates body temperature,
hunger, thirst, sexual response, circadian
rhythms
38The Telencepholon
- Cerebrum
- with cortex and corpus callosum
- higher thinking
39Cerebrum
40Cerebrum
41Cerebrum
42Limbic System
- Regulates emotions
- Association with different situations is done
mostly in the prefrontal lobe
43 Memory
- Short Term
- Done in the frontal lobe
- Long Term
- Frontal lobes interact with the hippocampus and
the amygdala to consolidate
44Sensory Receptors
- Mechanoreceptors
- Pain Receptors
- Thermoreceptors
- Chemoreceptors
- Electromagnetic Receptors
45Sensory Receptors
- Mechanoreceptors
- Pain Receptors
- Thermoreceptors
46Sensory Receptors
47Sensory Receptors
- Electromagnetic receptors
48Evolution of the Eye
- Complex eyes have developed many times
49Evolution of the Eye
- All light-sensitive organs rely on photoreceptor
systems employing a family of proteins called
opsins. Further, the genetic toolkit for
positioning eyes is common to all animals the
PAX6 gene controls where the eye develops in
organisms ranging from mice to humans to fruit
flies
50Photoreceptors
- Eye cups (ocelli) - light detection
- Genetic basis that started as a light detector
600 mya - During the Cambrian explosion around 540 mya two
types of eyes arose
51Photoreceptors
- Compound Eyes - made up of ommatidia that helps
detect movement
52Photoreceptors
- Camera Type Eyes Evolved several times
- Hagfish eye
- Lamprey eye
- Jawed vertebrate eyes
53(No Transcript)
54Single Lens Eye
- Sclera (white)
- Cornea (clear)
- Choroid (pigmented)
- Iris (color of eye)
- Retina (rods and cones)
- Pupil
- Fovea (focal point)
- Blind spot
55Photoreceptors
- Scars of Evolution
- 1. inside out retina that forces light to pass
through the cell bodies and nerves before hitting
the retina - 2. blood vessels across the retina that cause
shadows - 3. nerve fibers that exit causing a blind spot
56Focusing
- Near vision
- ciliary muscle contracted
- lens becomes more spherical
- Distance vision
- ciliary muscle relaxed
- lens becomes flatter
57Visual Problems
- Near-sightedness (myopia)
- eyeball too long / focal point in front of fovea
- Far-sightedness (hyperopia)
- eyeball too short / focal point behind fovea
- Astigmatism (blurred vision)
- misshapen lens or cornea
58Hearing and Equilibrium
59Hearing Organ
- Outer Ear
- pinna and the auditory canal
- tympanic membrane
- Middle Ear
- malleus, incus and stapes
- oval window
- Inner Ear
- cochlea with the Organ of Corti
- with a basilar membrane and hair cells
- Eustachian Tube
60Sound
- Volume
- amplitude of sound wave
- vibrates fluid in ear and bend hair cells which
generates more action potentials - Pitch
- frequency of sound wave
61Equilibrium
- Utricle and Saccule
- Semicircular Canals
- used to detect body position and movement
62Lateral Line System
- Similar to inner ear
- detects movement of current, moving objects
63Statocysts
- Equilibrium
- contain statoliths
64Sound Systems in Invertebrates
- Body hairs that vibrate
- mosquitoes
- Tympanic Membranes
- crickets
65Chemoreception
- Taste Buds
- sweet (tip), salty (behind), sour (sides), bitter
(back of tongue)
66Chemoreception
- Olfactory receptors cells
- upper portion of nasal cavity
67The Cost of Locomotion
68The Cost of Locomotion
- Locomotion must overcome two forces
- gravity
- friction
- Swimming is more efficient than running
- runner must overcome gravity
- Larger animals travel more efficiently than
smaller animals - Flight is the most costly (per minute)
69Skeletal Structures
- Hydrostatic Skeleton
- (cnidaria, ctenophora, platyhelminthes, nematoda,
annelida) - Exoskeletons
- mollusca, arthropoda
- Endoskeletons
- chordata
70Cooperation of Muscles and Skeletons
- Muscles always contract
- Muscles attached in antagonistic pairs
71Skeletal Muscles
- Muscles are made up of muscle fibers
- Fibers are made up of myofibrils
- Myofibrils are made up of myofilaments
- thin filaments (actin)
- thick filaments (myosin)
72Sliding Filament Model
- Sacromeres (basic functioning unit)
- Z lines (border of sacromeres)
- H zone (center of sacromere)
- I band (only thin filaments)
- A band (length of thick filaments)
73Sliding Filament Model
- During contraction, thin and thick filaments
slide past each other - I band and H zone decreases in size
- Caused by myosin head creating cross bridge with
actin fiber and then moves by using ATP
74Muscle Control
- Tropomyosin blocks myosin binding sites
- Calcium ions allow cross bridges to form
75Muscle Fibers
- Fast Muscle Fibers
- rapid, powerful contractions
- flight muscle
- Slow Muscle Fibers
- sustain, long contractions
- adductor muscles
76Invertebrate Muscles
- Flight muscles in insects are capable of
independent contractions - wings beat faster than action potentials
- Clam muscles contain paramyosin that allows them
to remain contracted with little energy - Nematodes only have longitudinal muscle that
gives them their characteristic movements