Nervous System Flashcards
(236 cards)
1
Q
What are the building blocks of the Peripheral nervous system?
A
Neurons
Nerves
Ganglia
Pathways
Circuits
2
Q
What are some important things to consider when thinking about nervous systems?
A
Direction of information
Location of the cell body
Connections
3
Q
What did the chordate nervous system evolve from?
A
A hollow tube
No proper eyes or brain
CNS = hollow tube with anterior bulge
4
Q
What do pharyngeal slits become?
A
Organisation of the head
5
Q
What is the dorsal hollow nerve tube?
A
Origin of CNS
6
Q
What are the chordate synapomorphies?
A
1) Pharyngeal slits –> Organisation of the head
2) Notochord
3) Dorsal hollow nerve tube –> Origin of CNS
4) Endostyle (–> Thyroid gland)
5) Post-anal tail
7
Q
What is a vertebrate?
A
Fancy chordate
8
Q
What are the vertebrate synapomorphies?
A
1) Vertebral column
2) Cranium
3) Neural crest
4) Neurogenic Placodes
5) Tripartite (three-part) brain (fore, mid, hind)
6) Hypothalamus-Pituitary system
9
Q
Why were the genes for neural crest, 3-part brain, neurogenic placodes allowed to diversify?
A
Due to genome duplication
10
Q
Why is the Nervous System segmented?
A
Because Chordates are segmented
11
Q
Where can nerves arise from?
A
The brain or the spinal cord
12
Q
What are nerves that arise from the Brain called?
A
Cranial nerves (CN)
13
Q
What are nerves that arise from the Spinal cord called?
A
Spinal Nerves (SN)
14
Q
What are the two components of the peripheral nervous system?
A
Somatic
Visceral
15
Q
What is the Somatic part of the peripheral nervous system?
A
Skeletal muscles, skin and derivatives of those
Connect directly to target
16
Q
What is the visceral part of the peripheral nervous system?
A
Connects to walls of internal organs, involuntary muscles, glands
Visceral neurons connect via a peripheral autonomic ganglion.
17
Q
What unique chordate feature gave rise to the Central Nervous System?
A
Dorsal Hollow Nerve Cord
18
Q
How are neurons classified (basically)?
A
Sensory
(afferent)
Motor
(efferent)
Interneuron
19
Q
What is the function, distribution and location of the Sensory Neuron?
A
Visceral
- Special - CN
- General - CN + SN
Somatic
- Special - CN
- General - CN + SN
20
Q
What is the function, distribution and location of the Sensory Neuron?
A
Visceral
- CN and SN
Somatic
- CN and SN
21
Q
What is the function, distribution and location of the interneuron?
A
Relay/integration
CNS
22
Q
What do cranial nerves carry?
A
Special and General sensory
23
Q
What do Spinal nerves carry?
A
Exclusively general sensory
24
Q
What are the components of the visceral efferent part of the Autonomic NS?
A
Motor
Parasympathetic and Sympathetic
- Motor
25
What are the components of the visceral afferent part of the Autonomic NS?
Sensory
26
What are the components of the somatic nervous system?
Motor
Sensory
27
What are sympathetic and parasympathetic? How do they reach target?
Usually antagonistic
Generally, reach the target via the ganglia
28
What does the Sympathetic NS do?
Sympathetic Chain
(Aka sympathetic trunk, paravertebral ganglia)
Prepares for activity "fight or flight"
29
What does parasympathetic ns do?
Vagus nerve (75%)
+ Sacral spinal nerves
Homeostasis ("rest and digest")
30
What can nerves contain?
Mixtures of somatic, visceral, motor, and sensory
31
What are some important things to consider when looking at the basic descending circuits involving the PNS?
Direction of information
Location of the cell body
Connections
32
Where are the PNS cell bodies?
In CNS or in peripheral ganglia
33
What is the visceral motor?
Parasympathetic
or
Sympathetic
34
What are the 3 basic pathways involving PNS?
Reflexes
Ascending pathways
Descending pathways
35
What is the general structure of a spinal nerve?
Central canal
Ventral horn of grey matter (motor)
Dorsal horn of grey matter (sensory)
White matter
Dorsal root
Ventral root
Spinal ganglion
Interneurons
Somatic motor neurons
Visceral motor neuron (pre-ganglionic)
Grey communicating ramus
Visceral motor neuron (post-ganglionic)
Visceral sensory neuron
Splanchic nerve to gut
Sympathetic ganglion
White communicating ramus
Spinal nerve
Somatic motor neuron
Somatic sensory neuron
Ventral ramus of spinal nerve to muscles, glands and skin
Dorsal ramus of spinal nerve to muscles, glands and skin
Cell bodies of sensory neurons
36
What is the general structure of a cranial nerve?
Sensory nucleus
Fourth ventricle
Sulcus limitans
Motor nucleus
Dorsal cranial nerve
Ventral cranial nerve
Sensory:
- Octavolateralis neurons (special somatic sensory)
- General somatic sensory neurons
- General or special visceral sensory neurons
Motor:
- Visceral motor neurons (autonomic nervous system)
- Somatic motor neurons (to branchiomeric muscles)
- Somatic motor neurons (to extrinsic ocular, epibranchial and hypobranchial muscles)
37
What is the spinal nerve in fish serving gill area like?
Sensory root and ganglion
Motor root
Pharyngeal ramus
Pretrematic ramus (visceral sensory)
Posttrematic ramus (sensory and motor)
Pharyngeal slit
38
Describe the spinal nerve of a Lamprey:
Dorsal spinal nerve (intersegmental)
Somatic sensory neuron
Visceral sensory neuron
Visceral motor neuron
Visceral ramus
Somatic motor neuron
Ventral spinal nerve
(segmental)
Myotome
39
Describe the spinal nerve of a Lissamphibian:
Dorsal root
Somatic sensory neuron
Visceral sensory neuron
Visceral motor neurons
Spinal nerve
Somatic motor neuron
Ventral root
40
Describe the spinal nerve of an Amniote:
Dorsal root
Spinal ganglion
Somatic sensory neuron
Visceral sensory neuron
Spinal nerve
Visceral motor neuron
Somatic motor neuron
Ventral root
41
What were spinal nerves orginally for?
Activating repeated muscle blocks:
Repeated myomeres in cephalochordates
Segmented epaxial muscle in mammals
Also in fish - Epaxial muscles (dorsal ramus), Hypaxial muscles (Ventral ramus)
Hypaxial muscle evolved high complexity --> Complex innervation
42
What are the cranial nerves?
Olfactory nerve I
Oculomotor nerve III
Trochlear nerve IV
Abducens nerve VI
Vestibulocochlear nerve VIII
Hypoglossal nerve XII
Accessory nerve XI
Optic nerve II
Trigeminal nerve V
Facial nerve VII
Glossopharyngeal nerve IX
Vagus nerve X
43
What are the basic categories of CNs?
1) Sensory nerves unique to head (optic, olfactory, lateral line)
2) Ventral cranial nerves
3) Dorsal cranial nerves
44
What are the origins of cranial nerves?
Slits for filter feeding
-->
Slits to support gills
-->
Muscles, vessels and nerves for gill function
-->
Cranial muscles, nerves and aortic arches
-->
Pharyngeal arches
45
How have the cranial nerves evolved?
General ancestral pattern persists
CNS remain paired with the respective pharyngeal arch musculature
46
How did the cranial nerves evolve in Tetrapods?
Vomeronasal organ
(from olfactory nerve)
New glands evolve (e.g. salivary, lacrimal, mucosal)
47
How did the cranial nerves evolve in Amniotes?
Loss of lateral line system
Optic nerve decussates
Mammals and Birds have developed a cochlea
48
How did the autonomic nervous system evolve in Agnathans?
Fragmentary ANS
Have sympathetic fibres, but no sympathetic chain
Parasympathetic in the vagus only
49
How did the autonomic nervous system evolve in Gnathostomes?
Chondrichthyes - sympathetic ganglia, but not linked in a chain
50
How did the Autonomic nervous system evolve in Tetrapods?
Have sympathetic trunk/chain
Feeding on land requires glands --> demand for parasympathetic in other Cranial Nerves.
51
How did the autonomic nervous system evolve in mammals and birds?
Developed ANS
Prevalent sympathetic ganglia
Visceral organs have parasympathetic and sympathetic
Mammals have enteric NS
52
What is the location of the cell body in CNS of the parasympathetic NS?
Hindbrain and sacral spinal cord (craniosacral)
i.e. CNs and SNs
53
What is the location of the cell body in CNS of the Sympathetic NS?
Thoracic and lumbar regions of spinal cord (thoracolumbar)
i.e. SNs only
54
What is the location of the ganglia in the Parasympathetic NS?
Close to target organ
55
What is the location of the ganglia in the Sympathetic NS?
Close to spinal cord
56
What is the length of the preganglionic axons in the parasympathetic NS?
Long
57
What is the length of the preganglionic axons in the sympathetic NS?
Short
58
What is the length of the postganglionic axons in the parasympathetic NS?
Short
59
What is the length of the postganglionic axons in the sympathetic NS?
Long
60
What is the preganglionic neurotransmitter in the parasympathetic NS?
Acetylcholine
61
What is the preganglionic neurotransmitter in the sympathetic NS?
Acetylcholine
62
What is the postganglionic neurotransmitter in the parasympathetic NS?
Acetylcholine
63
What is the postganglionic neurotransmitter in the sympathetic NS?
Norepinephrine
64
What information is carried in the dorsal root of the spinal cord?
Sensory (afferent) information INTO the CNS
65
What information is carried in the ventral root of the spinal cord?
Transmits signals from motor neurons in the spinal cord to the
- Skeletal muscles - Somatic motor
- Smooth muscle, cardiac muscle and glands - autonomic motor
66
Where are the ganglia for the sympathetic NS found?
Close to spinal cord
67
What cranial nerve is mainly responsible for parasympathetic activity?
Vagus nerve
Slows heart rate
Promotes digestion
Regulates respiration
Influences glandular secretions
68
What is a key difference between the preganglionic fibres of the sympathetic versus parasympathetic systems?
Length of preganglionic axons - long in Parasympathetic, short in sympathetic
Length of postganglionic axons - short in parasympathetic, long in sympathetic
Location of ganglia - Parasympathetic close to target organ, sympathetic close to spinal cord
69
What are the two reccurring themes?
1. Regional differentiation along A-P body axis
2. Biological control systems work in antagonistic pairs
70
What are three examples of the regional differentiation along the A-P body axis recurring theme?
Regions of the digestive tract
Regions of the spine
Regions of the Nervous System
71
What are three examples of the biological control systems work in antagonistic pairs recurring theme?
Antagonistic muscles
- e.g. triceps - elbow flexion <-- biceps
Antagonistic hormones
- e.g. insulin - blood sugar <-- Glucagon
Antagonistic autonomic nerve actions
- e.g. parasympathetic activity - blood flow to stomach <-- sympathetic activity
72
What is the role of the CNS?
The central nervous system coordinates activities that enable an organism to survive and reproduce in its environment
CNS receives sensory information from several sources
Interoceptors gather information related to organs and internal environment
Exteroceptors gather information from the external environment
information is then sent to effectors
73
Why is an understanding of embryological development important?
Helps us to understand brain structure across adult species
74
What happens in gastrulation?
Fertilisation results in the formation of a blastula - a sphere of cells around a central cavity
Cell proliferation process in which cell groups are organised by fate
75
What does the ectoderm form?
Skin and nervous tissue
76
What does the endoderm form?
Surrounds cavity that will become the lumen of the gut
77
What do the notochord and part of mesoderm become?
Induce the formation of the neural tube
78
What do you see in a transverse section through the body of a developing vertebrate?
Endoderm encircles the gut
Neural tube is closing and will separate from the ectoderm
Inner space of neural tube will form the ventricular system; CNS will develop within the walls
79
What are the components of a transverse section through the body of developing vertebrate?
Notochord
Neural fold
Presumptive neural tube
Epidermis
Endoderm
Archenteron (gut)
Lateral plate mesoderm (hypomere)
Intermediate mesoderm (mesoderm)
Somite (epimere)
Migrating neural crest cells
80
What happens in neurulation?
A portion of the ectoderm thickens and forms the neural plate.
A pair of neural folds develops along the plate (neural folds on either side of the neural groove), the folds grow together dorsally and form a neural tube
81
What do we know about the segmental development of the vertebrate brain?
3 embryonic regions differentiate from the anterior neural tube (rostral to caudal):
Prosencephalon
- Forward brain, forebrain
Mesencephalon
- Middle brain, midbrain
Rhombencephalon
- 'rhomb' referring to the rhomboid shape of its ventricle - becomes the hindbrain
82
What does the Prosencephalon become?
Telencephalon
- Cerebrum
Diencephalon
- Eye cup
- Thalamus
- Hypothalamus
- Epithalamus
83
What does the mesencephalon become?
Mesencephalon
- Midbrain
84
What does the rhombencephalon become?
Metencephalon
- Pons
- Cerebellum
Myelencephalon
- Medulla oblongata
85
What kind of tissue is the retina?
Neural tissue
Comes from optic vesicles which are part of the forebrain
86
What happens when the telencephalon and diencephalon differentiate?
Form the cerebral hemispheres (telencephalon)
Form the diencephalon, optic cups and olfactory bulbs (diencephalon)
Form the lateral ventricles and then the third ventricle
Grey matter structures: Then form the cerebral cortex, thalamus, hypothalamus and basal telencephalon
White matter structures: Finally, forms the corpus callosum, cortical white matter and internal capsule
87
What are the forebrain structure-function relationships?
The forebrain is the seat of perceptions, conscious awareness, cognition and voluntary action.
This requires extensive interconnections with the sensory and motor neurons of the brain stem and spinal cord
The thalamus is the gateway to the cerebral cortex
Sensory pathways from the eyes, ears and skin all relay in the thalamus before terminating in the cerebral cortex
88
What does the hypothalamus do?
Regulates the ANS - important for fight or flight
89
How does the midbrain differentiate?
The dorsal surface becomes the tectum
Floor becomes the tegmentum
- Tectum
- Cerebral aqueduct
- Tegmentum
90
How does the caudal hindbrain differentiate?
The caudal hindbrain differentiates into the medulla
The medullary pyramids are bundles of axons coursing caudally toward the spinal cord
The CSF-filled space at the core of the medulla is the fourth ventricle
Corticospinal tract - also called pyramidal tract
91
What happens near where the medulla joins the spinal cord?
The pyramidal tracts cross the midline, forming the pyramidal decussation
This means that the cortex on one side of the brain controls movement on the other side of the body
92
What happens in differentiation of the spinal cord?
Spinal canal
Dorsal horn
- Sensory input - receives sensory inputs from dorsal root fibres
Ventral horn
- motor output - cells project to ventral roots that innervate muscles
93
What structures does the prosencephalon differentiate into?
Telencephalon
- Cerebrum
Diencephalon
- Eye cup
- Thalamus
- Hypothalamus
- Epithalamus
94
Where does sensory information enter the spinal cord?
Through the dorsal roots of spinal nerves
95
What germ layer develops into the CNS?
Ectoderm
96
You reach for a glass of water with your left hand. Which side of the brain initiates this action?
Right Hemisphere
97
What is the meninges?
Brain and spinal cord are encased in protective meninges
In fish - single membrane
In mammals - three layers
- Dura matter
- Arachnoid layer
- Pia matter
98
What is the structure of the meninges in fish?
Single membrane
99
What is the structure of the meninges in mammals?
Three layers
- Dura matter
Subdural space
- Arachnoid layer
Subarachnoid space
- Pia matter
100
What are the parts of the ventricular system?
Olfactory bulb
Olfactory ventricle
Telencephalon
Lateral ventricles
Third ventricle
Diencephalon
Tectal ventricle
Midbrain tectum
Hypothalamic recess of third ventricle
Cerebral aqueduct
Cerebellar ventricle
Cerebellum
Fourth ventricle
Hindbrain
Spinal cord
Central canal
101
What are the two major functions of the spinal cord?
Transmissions of neural signals
Coordination of spinal reflexes
102
What is the basic mechanism of a spinal reflex?
Stimulus
Sensory neuron
Relay neuron
Motor neuron
Motor neuron
Effector
103
What do we know about the spinal tracts?
Most info is not processed at the spinal cord level
Fibres carrying similar information tend to travel together
Nerve tracts may be ascending or descending
104
What are the most prominent ascending tracts of the spinal cord?
Fasciculus gracilis and fasciculus cuneatus
Located in the dorsal spinal cord
Both carry proprioception info
105
What do we know about the descending tracts of the spinal cord?
Transmit infor from the brain to the spinal cord
An important one is the corticospinal tract: Cerebral cortex to motor neurons controlling limbs - places skeletal muscle under cerebral control
Tectospinal tract: Visual and auditory stimuli from the tectum
Rubrospinal tract: Midbrain to spinal cord
106
Differences in size of the telencephalon across species?
Reptiles - medium
Birds - Large
Mammals - Large
Amphibians - small
Fish - very small
107
What is the hindbrain?
Location of primary nuclei for some cranial nerves (VII-XII in mammals; V-X in sharks)
Major route of passage for ascending and descending pathways
Contains major centres for involuntary reflexes: E.g. visceral, auditory, and proprioceptive reflexes - important for regulating HR, BP and intestinal mobility
108
What does the hindbrain differentiate into?
Rhombencephalon (Hindbrain)
Metencephalon
- Pons
- Cerebellum
Myelencephalon
- Medulla oblongata
109
What is the pons?
Hindbrain
Critical relay centre for sensory and motor tracts between the cerebral cortex and cerebellar cortex
110
What is the cerebellum?
Dorsal extension of the metencephalon - can be highly convoluted
111
What are the main functions of the cerebellum?
Modifies and refines motor outputs - does not initiate motor output
Important for maintaining equilibrium
Important for refining motor activity
112
What are the differences in size of the cerebellums of different species?
Amphibian
- Tiny
Reptile (alligator)
- Small
Bony fish (trout)
- Medium
Primitive fish (dogfish shark)
- Medium
Bird (pigeon)
- biggish
Small mammal (rabbit)
- bigger
Large mammal (horse)
- Very big
113
What is the brain structure of the amphibian?
Olfactory bulb
Cerebrum
Optic lobe
Cerebellum
Pituitary
114
What forms the midbrain?
The mesencephalon
115
What is the diencephalon comprised of?
Epithalamus
Hypothalamus
Ventral and dorsal thalamus
116
What does the epithalamus include?
The pineal gland and habenular nucleus
117
What is the hypothalamus home to?
A constellation of nuclei that regulate homeostasis to maintain physiological balance
118
What is the ventral thalamus?
A small area between midbrain and thalamus
119
What is the dorsal thalamus?
Houses nuclei receiving sensory inputs - major coordinating centre of incoming sensory inputs all over the body
120
What is the telencephalon?
A pair of lobes (cerebral hemispheres), plus the olfactory bulbs
Corpus collosum
121
What are the layers of the telencephalon called?
The cortex or cortical region
Subcortical region
122
What does the cerebrum do?
Processes sensory information from the thalamus
123
What is the cortex like in many mammals?
Folded to accommodate its increased size - the folds are called gyri and the crevices are sulci
124
What do you see in a transverse section through cerebral hemispheres?
Evaginated hemispheres as seen in cartilaginous fishes
Everted hemispheres as seen in ray-finned fishes (actinopterygians)
125
What would happen if you removed an animal's cerebellum?
Severe loss of coordination (ataxia)
Balance and posture problems
Impaired eye movements
Normal sensation and strength
126
What parts of the brain might be activated in response to suddenly seeing a predator?
Sympathetic nervous system activated
Fight or flight coordinated by hypothalamus
127
Give examples of a stimulus:
Light
Mechanical
Chemical
Electrical
128
Give examples of a sensory organ:
Lateral line
Heat organ
Echolocation
Hearing
Eye sight
Infrared sight
Vibration sensors
Golgi organs
Spindle organs
129
What is the role of the CNS?
Interpretation
130
What are generalised sensory receptors?
Usually transducers
They convert signals from one type to another
Sensory nerve fibre + amplifier = sensory organ
131
What are the three types of general sensory organ?
Free sensory receptor
Associated sensory receptor
Encapsulated sensory receptor
132
What do free sensory receptors do?
Respond to these stimuli:
- Pain, extreme temperature
- Touch/pressure
- Chemical
E.g.
- Tooth ache
- Capsaicin (spicy)
133
Where are free sensory receptors located?
High sensitivity areas
e.g.
Skin
Cornea
Oral cavity
Tooth pulp
Intestines
134
What do encapsulated sensory receptors do?
Respond to stimuli like:
- Touch
- Pressure
- Vibration
- Warm/cold
E.g.
- Meissner's corpuscles
- Pacinian corpuscles
- Merkel's disks
- Ruffini's corpuscles
135
Where are encapsulated sensory receptors located?
Dermis
Pancreas
136
What do associated sensory receptors do?
Respond to these stimuli:
- Proprioceptive (relative location in space)
- Mechanical
e.g.
- Hairs
- Golgi tendon organs
- Muscle spindles
137
What is proprioception?
Based on info gathered by receptors in muscles, tendons and joints
Used to adjust posture and pre-activate muscles in preparation for an action (e.g. landing after a jump, catching oneself after tripping)
138
What are muscle spindles in terms of proprioception?
Specialised muscle cells - intramural
Regulating resting muscle tone
Stretch reflex
139
What is the mechanism of the stretch reflex coordinated by the muscle spindles?
A.
- Sensory nerve
- Spinal cord
- Muscle spindle
- Extrafusal muscle cell
B.
- Motor nerve
C.
- Relaxed muscle spindle
- Contracting muscle
140
What are Golgi tendon organs in terms of proprioception?
Within tendons of skeletal muscles
Tension recorders
141
What are chemoreceptors?
Respond to these stimuli
- Chemical
- Odours
Sensory organ
- Chemoreceptors
- Nasal passages
- Mouth
- Skin
- Fins
CNS
- Smell?
- Taste?
142
What is the difference in olfaction across species?
Amphibian
- Large olfactory bulb
Fish
- Olfactory bulb
- Olfactory tract
Reptile
- Olfactory bulb
- Olfactory tract
Mammal with smooth cortex (rabbit)
- Olfactory bulb
- Olfactory tract
Mammal with convoluted cortex (cat)
- Olfactory bulb
Mammal (primate)
- Olfactory bulb
- Olfactory tract
143
What do the chemoreceptors in the human gustatory system detect?
Sweet
Salty
Sour
Bitter
Savoury
144
What about pheromones? Importance? Receptors?
Important for inter-individual communication
(Chemo)Receptors are located in the vomeronasal organ
145
Describe the cat vomeronasal organ:
Odours enter nasal passage
Vomeronasal organ
Olfactory epithelium
Accessory olfactory bulb
Brain
Sites in medial amygdala that link to hypothalamus
146
What does the vomeronasal organ do?
Odour particles are captured from the air by the tongue
Odour particles mixed with fluids in the mouth are delivered to the ducts leading to the vomeronasal organs
147
What are radiation receptors?
Respond to these stimuli
- Electromagnetic waves
Sensory organ:
- Eyes (UV; fishes, reptiles, birds, mice)
- Eyes (visible light)
- Pit organs (infrared; vampire bats, python, pit vipers)
CNS:
- Vision
- Direction
148
What species have eyes that can detect UV light?
Fishes
Reptiles
Birds
Mice
149
What are pit organs? Which species have them?
Organs which can detect infrared light
- Vampire bats
- Python
- Pit vipers
150
What are photoreceptors?
Detect visible light: 380-760nm
151
What do rods detect?
Light intensity
152
Which species have rods?
All vertebrates
153
What do cones detect?
Colour
154
Which species have cones?
Earliest vertebrates had 4 cones:
- Violet
- Blue
- Green
- Orange
Fish, Turtles, lizards and birds all have tetrochromatic vision
155
Which species have tetrochromatic vision (4 cones)?
Fishes
Turtles
Lizards
Birds
156
Which species still has monochromatic vision?
Amphibians
157
What is the anatomy of the eye?
Eyelid
Suspensory ligament
Lens
Cornea
Iris
Anterior chamber
Posterior chamber
Ciliary body
Vitreous body
Optic nerve
Fovea
Retina
Choroid
Sclera
158
What is the cellular level of the retina of the eye?
Retina:
- Ganglion cell
- Amacrine cell
- Bipolar cell
- Horizontal cell
- Rod
- Cone
- Pigment layer
Choroid
Sclera
159
What are the parts of a lamprey eye?
Lens
Iris
Spectacle
Cornea
Corneal muscle
Choroid
Retina
Blood sinus
160
What are the parts of a shark's eye?
Protractor lentis muscle
Lens
161
What are the parts of a teleost eye?
Suspensory ligament
Conjunctiva
Iris
Retractor lentis muscle
Scleral cartilage
Sclera
Choroid
Retina
Optic nerve
162
What are the parts of an amphibian eye?
Lens
Protractor lentis
Suspensory ligament
Cornea
Nictitating membrane
Lower eyelid
Conjunctiva
Optic nerve
Retina
Choroid coat
Sclera
163
What are the parts of a lizard eye?
Lens
Cornea
Iris
Scleral ossicle
Vitreous body
Sclera
Choroid
Retina
Fovea
Papillary cone
Optic nerve
Ciliary muscle
164
What are the parts of a bird's eye?
Lens
Cornea
Iris
Ciliary muscle
Scleral ossicle
Vitreous body
Choroid
Fovea
Retina
Pecten
Optic nerve
Sclera
Suspensory ligament
Ciliary body
165
How does the eye change in species which must see underwater?
Large difference in refractive indices between air and the eye
Cornea and water have similar refractive indices
Therefore aquatic vertebrates rely more heavily on the lens for focussing
166
Why do fish deep in the sea still have eyes?
Light intensity low/zero underwater.
Fish still have eyes as they respond to bioluminescent light and use to to receive or send signals
167
What do we know about the pineal complex?
Consists of the pineal gland, which is part of the epithalamus.
Photosensitive organ
Some turtles may be able to detect light through pineal gland
Acts as a biological clock
Lack of pigment and thin skull region may act as a skylight to the brain
168
What do we know about magnetoreception?
Some animals, like turtles, can sense a magnetic field and use it as a compass
Two theories:
- Some animals have magnitite which is like a magnetic sensor
- Some birds may possess cryptochrome protein in their eyes which could allow them to 'see' magnetic field - like pigeons
169
What do we know about infrared receptors?
4 groups of vertebrates can detect IR - vampire bats and snakes like pit vipers, pythons etc
Depends on genes TRP-A1 in snakes, in Bats, TRP-B1.
Have pits for IR detection
Pit IR receptors around nose in bats, under eyes in snakes
170
What are the components of the IR pits?
Scale
Air-filled outer cavity
Pit membrane
Air-filled inner cavity
Trigeminal afferent
171
What happens in mechanoreception?
Detect water currents, maintain balance, hear sounds
Hair cells
Neuromast organ
172
What do we know about the lateral line system in neuromasts?
Consists of long grooves or channels called lateral lines
They are flow sensing organs
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How do lateral line system neuromasts work?
Respond to water current
Orientation of hair cells
'distance touch'
Neuromast cells oriented with the most sensitive axis parallel to the lateral line canal
Moving in one direction, the firing rate will increase - how they detect flow
174
How do blind cave fishes use lateral line neuromasts?
Blind cave fishes can navigate using this
Flow can even tell them information about prey animals on the surface of the water
175
What do we know about the vestibular system?
Developed from part lateral line system
Uses hair cells, balancing organ
Fluid filled system of channels contains semicircular canals
Sensory receptors in the canals called cristae
Respond to rotation, angular acceleration produced by head movement in ear canals, detected by fluid moving over hair cells
CNS told whether at rest or in motion by the orientation affecting the fluid
Also has a sound reception section
176
How many semicircular canals are in the vestibular system of jawed vertebrates?
3
Anterior
Posterior
Horizontal
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What are the components of the vestibular system?
Endolymphatic duct
Semicircular canals
- Horizontal
- Posterior
- Anterior
Crista ampulla
Macula neglecta
Macula lagena
Lagena
Organ of corti
Cochlea
Macula sacculus
Sacculus
Macula utriculus
Utriculus
Cristae ampullae
b. Crista
Wall of ampulla
Crista
Cupula
Hair cell
Nerve fibres
c. Macula
Otoconia
Gelatinous matrix
Hair cell
Supporting cells
Nerve fibres
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What do we know about the external ear?
Present in mammals
Absent in fishes or amphibians
179
What are the components of the human auditory system?
Malleus
Semicircular canals
Inner ear
Cochlea
Eustachian tube
Middle ear
Stapes
Incus
Outer ear
Ear canal
Ear drum
180
What do we know about the auditory system of owls?
Evolved to improve auditory reception
Tightly packs raised limb of facial feathers act as a sound capturing device and channel the sound into the ear
Left and right external orifices are different in size and shape, one up one down - creates two ears with different acoustic qualities from any direction - localise the sound and detect the prey, e.g. mouse
181
How do bats use sound to navigate?
Echolocation
Make high pitched sound and listen to the echo to create a representation of their environment, like an image
182
What do we know about the star nosed mole?
North american, east coast, swampy habitats
Array of 22 appendages around nostrils
183
How does the star nosed mole use its star nose to navigate?
By feel
22 appendages around nostrils
Specialised skin surface dedicated to touch, raised domes - Eimer's organs
From the trigeminal nerve
Feel around and this generates a 3D image in their brain of their surroundings
They position their snout over the food to eat it
Significant part of their brain is dedicated to their sensory appendages
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What is the generic key function of a sensory organ?
Detect specific types of stimuli from the environment and convert them into electrical signals (nerve impulses) that the brain can interpret.
In simple terms, sensory organs act as transducers—they transform external physical or chemical inputs (like light, sound, temperature, or chemicals) into neural signals. Each sensory organ is specialised for a particular type of stimulus
185
How do animals use hair cells to detect changes in their environment?
Animals use hair cells as specialized sensory receptors to detect mechanical changes in their environment, such as sound, movement, or pressure. These cells are key to the senses of hearing, balance, and in some cases, water movement detection. Here’s how they work:
How Hair Cells Work:
- Structure: Hair cells have bundles of tiny hair-like projections called stereocilia on their surface.
- Mechanism: When the environment changes—like sound waves in the air or vibrations in water—these physical movements cause the stereocilia to bend.
- Signal Transduction: The bending opens ion channels in the hair cell’s membrane, causing an electrical signal to be generated.
- Neural Transmission: This signal is sent to the brain via a sensory nerve for interpretation.
Examples in Animals:
- Mammals (e.g., humans): Hair cells in the cochlea of the inner ear detect sound waves; hair cells in the vestibular system detect head position and motion.
- Fish and amphibians: Hair cells in the lateral line system detect water currents and vibrations, helping them sense nearby movement or obstacles.
- Insects: Some have hair-like structures sensitive to air movement or sound.
In essence, hair cells allow animals to convert mechanical stimuli into neural information, enabling them to respond to their surroundings.
186
Animals perform coordinated movements necessary for survival. Any examples?
Monkeys - Manipulate with hands
Hummingbirds - Hover
Cheetahs - Predators and Fast
Alligator - Sensory receptors on face detect small ripples of water
Frogs - Jump
All controlled or governed by the CNS
187
What is the sensorimotor cycle?
Sensors
- Use a variety of receptors
Information from the sensors sent to the brain and spinal cord
Brain and spinal cord then send the information to the musculoskeletal system
The musculoskeletal system then enacts a behaviour
The cycle continues
188
What are some examples of receptors in sensorimotor cycles?
Visual system
Inner ear
Innervated feathers (in birds)
189
What are the components of the ascending auditory system?
Hindbrain
Torus semicircularis
Telecephalic pallium
Dorsal thalamus
190
What are the components of the ascending visual pathway?
Dorsal thalamus
Telecephalic pallium
Optic tectum
191
What are the components of the somatosensory pathway?
Hindbrain
Dorsal thalamus
Somatosensory tectum
Telecephalic pallium
192
What are the components of the descending motor pathway, or corticospinal tract?
Reticular formation
Cerebellum
Midbrain tectum
Pretectum
Telecephalic pallium
193
How have amiotes adapted to life on land?
By evolving a wide range of movements
194
What is the cerebellum of birds and mammals like?
Large
Surface area is increased by folia
195
What are the flocculonodular lobes?
The vestibular centre in mammals
196
What is the flocculos important for?
Gait stabilisation in birds
197
What is the vermis?
Central body of cerebellum
Receives input from most sensory modalites
198
What do the Purkinje cells do in the brain?
Provide the only efferent signall from the cerebellum
199
What are some major efferent connections of the mammalian cerebellum?
Isocortex
Dorsal thalamus
Purkinje cell
Deep cerebellar nuclei
Vestibular nuclei
Red nucleus
200
What are the major sensory pathways in the mammalian brain?
Ascending sensory pathways
Descending pathways
201
What have the ascending sensory pathways evolved to do?
Carry sensory info more directly to the dorsal thalamus and cortex
202
What carries sensory info to the cortex?
The 3-neuron chain
203
What is the 3 neuron chain?
Chain of neurons which carry sensory info into the cortex
Primary sensory neurons
Secondary sensory neurons
Tertiary sensory neurons
204
What do the primary sensory neurons do?
Terminate on interneurons in the dorsal horn or sensory nuclei of cranial nerves
205
What do the secondary sensory neurons do?
Continue from the dorsal horn, or brainstem
206
What do the tertiary sensory neurons do?
Travel from dorsal thalamic nuclei through the internal capsule to terminate in the primary sensory cortex
207
What happens to the signals as they travel through the three neuron chain?
They are enhanced
208
What is the general rule of sensory info in the sensory cortex?
Sensory info is projected topographically upside down in the primary sensory cortex
209
What is topography related to?
The density of receptors
210
What do you know about anatomical proportions vs cortical magnification?
Some species have a lot more space focussed on their sensory areas.
If they were to be drawn with this magnified, they would have huge 'homunculus' features.
E.g. star nosed mole would have huge appendages
They are magnified in terms of relative magnification on the cortex of different sensory areas
211
What are the retinal fibres like in the mammalian optic system?
Many remain ipsilateral - unlike other vertebrates that mostly decussate at the optic chiasm
212
What is decussation?
Relates to the binocular overlap
Decussation refers to the crossing of nerve fibers from one side of the central nervous system (CNS) to the other.
213
Where do optic fibres in the retina project to?
Retina --> Project to the Lateral geniculate nucleus VGN
--> Project to the primary visiual cortex - V1
214
What does the primary visual cortex, V1 do?
Analyses colour, pattern, and depth
215
What does the optic tract project to?
Optic tract/extrastriate cortex --> Project to the superior colliculus --> project to the pulvinar --> Project to the extrastriate cortex
216
What does the estrastriate cortex do?
Visual attention and motion
217
What are some visually related reflexes?
Head/eye movements toward unexpected stimulus
Pupillary and accommodation reflexes
218
What does motor control do?
Allows vertebrates to maintain posture, control locomotion, balance
Groups of neurons in the brainstem and spinal cord control reflexes, rhythmic movements during locomotion etc.
219
What do descending pathways do?
Initiate and modulate motor activity
220
What are some components of the descending (motor) pathway?
Corticospinal tract
Isocortex
Olfactory cortex and limbic system
Striatum
Substantia nigra and tegmental nuclei
Reticular formation
Reticulospinal tract
Cerebellum
Subthalamus
Dorsal thalamus
Superior colliculus
Habenula
221
What is the function of the rubrospinal tract?
Motor function
Facilitates activity of flexor muscles and inhibits activity of extensor muscles
222
What is the function of the tectospinal tract?
Coordinated locomotor and feeding movements
Reflex head turning
Reflex postural movements in response to visual stimuli
223
What is the function of the vestibulospinal tract?
Maintain equilibrium reflexes using vestibular apparatus input
Postural reflexes
Facilitates the activity of the extensor muscles
224
What is the role of the reticulospinal tract?
Control proximal and axial muscles and to be involved mainly in gross movements such as locomotion, reaching and posture
225
What is the role of the corticospinal tract?
Involved in fine control, particularly of independent finger movements
226
What is the Pyramidal System?
Direct pathway from the neocortex to motor centres in the brainstem and spinal cord - called the corticobulbar tract and corticospinal tract
227
What does the pyramidal system enable?
Execution of complex, voluntary motor activities with precision
For humans, this includes speech, fine control, and tool use, like playing an instrument or playing sport
Purposeful and voluntary - performance improves with practice
228
What are the components of the pyramidal system?
Primary motor cortex
Cerebral peduncle via internal capsule
Corticobulbar
- Cranial nerve motor nuclei
Corticospinal (form pyramids)
- Motor (ventral) horns of the spinal cord
229
What does a human homunculus look like?
Lips, tongue and hands abnormally large as lots of neurons are present
230
What are the four lobes of the cortex?
Not well defined in many mammals
Parietal Lobe
Primary somatosensory cortex (S1)
Frontal Lobe
Primary motor cortex (M1)
Temporal Lobe
Primary auditory cortex (A1)
Occipital Lobe
Primary visual cortex (V1)
231
Where is the Primary somatosensory cortex (S1)
Parietal lobe
232
Where is the Primary motor cortex (M1)?
Frontal lobe
233
Where is the Primary auditory cortex (A1)?
Temporal lobe
234
Where is the Primary visual cortex (V1)?
Occipital lobe
235
A large animal suddenly appears in your periphery. How is this information communicated to your brain?
1. Detection:
Rods in the peripheral retina detect motion/light change.
2. Transmission:
Signal travels via the optic nerve → optic tract.
3. Processing:
Superior colliculus (midbrain) triggers a fast, reflexive response (e.g., turning your head).
Lateral geniculate nucleus (LGN) → Primary visual cortex (V1) processes the image consciously.
4. Integration:
Amygdala evaluates threat.
Parietal and prefrontal cortices coordinate an appropriate reaction.
236
What descending pathway would you use for carrying out a complex surgery?
Corticospinal tract
