The brain and sensory perception

Question 1

what does the forebrain become

Answer 1

The Forebrain leads to the Telencephalon and Diencephalon

Question 2

what does the telencephalon become

Answer 2

The Telencephalon leads to the Cerebrum (including the cerebral cortex, white matter basal nuclei)

Question 3

what is the structure of the telencephalon

Answer 3

The right and left cerebral hemispheres are connected through the corpus callosum
Deep within the white matter are clusters of nuclei, the basal nuclei which are involved in motor planning

Question 4

what is the cerebral cortex used for

Answer 4

The Cerebral cortex is vital for perception, motion, and higher order functions
The cerebrum is the largest structure in the human brain and is essential for awareness, language, cognition, memory and consciousness

Question 5

what does the CNS develop from

Answer 5

The CNS develops from the hollow nerve cord, which gives rise to the narrow central canal of the spinal cord and the ventricles of the brain

Question 6

what fills the canal of the spinal cord and 4 ventricles of the brain

Answer 6

The Canal and 4 ventricles fill with cerebrospinal fluid filtered from blood and functions to cushion the brain and spinal cord to provide nutrients and remove wastes

Question 7

what are the two types of neuronal matter

Answer 7

The brain and spinal cord contain both Grey matter and White matter

• Grey matter is the neuron cell bodies, dendrites, and un-myelinated axons
• White matter is the myelinated axons

Question 8

What are the four regions of the cortex

Answer 8

Frontal lobe, temporal lobe, occipital love, parietal lobe

Question 9

what does the frontal lobe do

Answer 9

Frontal lobe: Motor cortex (Controls skeletal muscles), Prefrontal cortex (decision making, planning), Broca’s area (forming speech)

Question 10

what does the temporal lobe do

Answer 10

Temporal lobe: Auditory cortex (hearing), Wernicke’s area (comprehending language)

Question 11

what does the occipital lobe do

Answer 11

Occipital lobe: Visual cortex (processing visual stimuli and pattern recognition) and Visual association cortex (combining images and object recognition)

Question 12

what does the parietal lobe do

Answer 12

Parietal Lobe: Sensory association cortex (integration of sensory information) and Somatosensory cortex (sense of touch)

Question 13

what can happen when the frontal lobe is damaged

Answer 13

Frontal lobe damage may impair decision making and emotional responses but leave intellect and memory intact

The frontal lobes have a substantial effect on “executive functions”

Gage was an American railroad foreman known for having survived a traumatic brain injury caused by an iron rod that shot through his skull and obliterated the greater part of the left frontal lobe of his brain. Remarkably he recovered all his senses but his character changed

Question 14

what is Broca’s area

Answer 14

Broca’s area in frontal lobe is active when speech is generated– Patients with damage in this are can understand language, but cannot speak*

Question 15

what is Wernicke’s area

Answer 15

Wernicke’s area (posterior temporal lobe) is active when speech is heard– Damage to this area causes patients to be unable to understand language, though they can still speakBW

Question 16

how is the cerebral cortex lateralized

Answer 16

The right and left hemispheres of the brain show difference in functions called lateralization:

The left side of the cerebrum has a greater role in language, and it is more adept at math and logical operations

The right side appears to be more active in recognition of faces and patterns, spatial relations, and nonverbal thinking

When listening to music, it gets split. The left side decodes the speech. And the right side decodes the melodic content

Question 17

what does the Diencephalon become

Answer 17

The Diencephalon contains the Thalamus, Hypothalamus, Pineal gland, and Pituitary gland.

Question 18

what does the Thalamus do

Answer 18

The Thalamus acts as the relay centre for most sensory information

Question 19

What are the four functions of the hypothalamus

Answer 19

The Hypothalamus acts on Homeostasis and hormones with 4 main functions:

1. Tt controls Thermoreceptive neurons in heat loss centre (controlling vasodilation and sweating) and heat gain centre (controlling shivering) to maintain body temperature at 37ºC
2. It releases oxytocin and vasopressin (an anti-diuretic hormone) into the posterior pituitary glands (the “master gland”). And controls the hormone release from anterior pituitary gland (this includes growth hormones, thyroid stimulating hormone, FSH/LH, Adrenocorticotropic hormone; ACTH: HPA stress axis)
3. It regulates appetite (hunger and satiety centres)
4. circadian rhythms are coordinated by a group of neurons in the hypothalamus called the suprachiasmatic nucleus (SCN). SCN is a pacemaker (~24 hours) synchronizing the biological clock

Question 20

what does the Pineal gland do

Answer 20

The Pineal gland releases melatonin, which plays an important function in maintaining diurnal rhythms; capillaries form CSF

Question 21

what does the midbrain become, and what are the two parts of this structure

Answer 21

The Midbrain becomes the Mesencephalon which is the top part of the brainstem. Right under the Diencephalon
Has two parts the Tectum (ceiling) and the Tegmentum (floor)

Question 22

what does the tectum do

Answer 22

Superior and Inferior colliculi control sensory motor integration

Question 23

What does the Tegmentum do (5 things)

Answer 23

• The Substantia Nigra: is a major source of DA to the basal nuclei; required for initiating movements; degeneration leads to Parkinson’s disease.
• The Ventral Tegmental Area (VTA): has mesolimbic DA (nucleus acumbmens) reward; mesocortical projections
• The Periaquiductal gray (PAG): gate pain signals, rich in opioid receptors
• The Red Nucleus controls rhythmic movement and gait
• The Crus cerebri: descending motor efferents from cortex to pons, cerebellum and SC

Question 24

what does the hindbrain become

Answer 24

The Hindbrain slits into two parts

The Metencephalon which has the pons and cerebellum

And the Myelencephalon which becomes the Medulla oblongata

Question 25

what does the metencephalon contain

Answer 25

The Metencephalon contains the Pons and the Cerebellum

Question 26

what do the pons do

Answer 26

- Have lots of tracts to cerebral and cerebellar hemispheres - Raphe Nucleus: are a major sources of serotonin (5HT) in the brain; also controls respiration centres in the medulla oblongata; responsible for aggression and mood; is a major target for anti-depressants such as Selective Serotonin Reuptake Inhibitors (SSRIs) and controls sleep - The Locus Coerules is a major sources of norepinephrine (NE) in the brain; which is involved in arousal, alertness and attention

Question 27

what does the cerebellum do

Answer 27

The Cerebellum controls motor coordination and learned motor tasks

Question 28

what does the myencephalon contain

Answer 28

The Myencephalon is at the bottom of the brain stem and contains the Medulla Oblongata

Question 29

what does the medulla oblongata do

Answer 29

The Medulla Oblongata controls respiration and heart rate Information is provided to the medulla from the Baroreceptors located in the heart muscles, aorta and carotid arteries. The Medulla oblongata then affects the SA node.

Question 30

what are the four types of receptor

Answer 30

Receptors can be grouped based on the type of stimulus energy they transduce. There are four major categories: Mechanoreceptors respond to touch, hearing, balance, blood, pressure and pain Chemoreceptors respond to taste, olfaction, pain, blood pH Electromagnetic receptors are used for vision and navigation Thermoreceptors sense heat and pain

Question 31

what do mechanoreceptors do

Answer 31

They sense physical deformation caused by forms of mechanical energy This is used for our response to pressure, touch, stretch, motion, and sound The knee-jerk response is triggered by the vertebrate stretch receptor, a mechanoreceptor that detects muscle movement The receptive field is the region of skin which deformation can lead to the activation of mechanoreceptors.

Question 32

How are touch receptors distributed

Answer 32

The receptive field of a sensory neuron is the region that when touched, evokes a perception Receptive fields can vary in size and density The two point discrimination threshold is used to test the density of receptors Areas like the fingers, palms, toes, etc have a higher density of receptors. And have lower mean two-point discrimination thresholds

Question 33

what do primary sensory neurons do

Answer 33

The cell bodies of primary sensory neurons are located in the DRG (PNS) Sensation from most of the body is mediated by 31 pairs of spinal nerves The Cranial nerve V (trigeminal) transmits sensations from the head)

Question 34

what do secondary and third-order neurons

Answer 34

Second-order neurons relay responses from the SC to the thalamus Third-order neurons relay information from the thalamus to the somatosensory cortex

Question 35

what does the Somatosensory cortex have

Answer 35

The Somatosensory cortex has different areas for each region of the body, bigger areas correlate to areas with more receptors higher importance, like the hands.

Question 36

what are pain receptors like

Answer 36

In humans pain receptors aka nociceptors, detect stimuli that reflect a harmful condition They respond to excess heat, pressure, or chemicals released from damaged or inflamed tissues

Question 37

how do animals see light

Answer 37

Animals use a diverse set of organs for vision. But the underlying molecules (pigments) for capturing light are the same, suggesting a common evolutionary origin Light detectors in the animal kingdom range from simple clusters of cels that detect the direction and intensity of light, to complex organs that form images Light detectors all contain photoreceptors, cells that contain light-absorbing pigment molecules

Question 38

what are ocelli

Answer 38

Most invertebrates have a light-detecting organs One of the simplest light detecting organs is that of a planaria A pair of ocelli called eyespots located near the head this allows planarians to move away rom light and seek shaded locations

Question 39

what are compound eyes

Answer 39

Insects and Crustaceans have compound eyes which consist of several thousand light detectors called ommatidia Compound eyes are very effective at detecting movement Some insects have excellent colour vision, and some can see in the UV range

Question 40

what are single lens eyes

Answer 40

Single lens eyes found in some jellies, polychaetes, spiders, and many molluscs They work on a camera-like principle The iris changes the diameter of the pupil to control how much light enters Eyes of all vertebrates have a single lens

Question 41

how do animals convert light into graded electrical signals

Answer 41

In the dark, high cyclic GMP (cGMP) keeps cGMP-gated cation channels (Epot = 0 mV) open. So, photoreceptor cells are depolarized in the dark. Light activates rhodopsin-G-protein cascade-closure of cGCMP channels. Causes the channel to close, which then causes a hyper-polarization The hyper-polarization is graded based on intensity of light

Question 42

how do octipi and human eyes differ

Answer 42

In the human eye, the light has to travel through the nerve fibers before it can hit the photoreceptor cells It also has a blind spot where all the nerve fibers converge into the optic nerve. Requires high metabolic rate In the Octopus eye, the photoreceptors are in front of the nerve fibers. So they don’t have a blind spot, and light can hit the photoreceptors directly. Doesn’t require high metabolic rate.

Question 43

how is the distribution of photoreceptors in the human body

Answer 43

around 5 million cones there is a concentration in fovea, region about 1.5 mm in diameter Most acute vision limited to foveola, covering ~0.4 mm (easy to see stuff directly in your vision)

Question 44

what is retinal circuitry like

Answer 44

5 types of neurons: photoreceptors, bipolar cells, ganglion cells, horizontal cells, and amacrine cells Form a Retinotopic map Vertical pathways are excitatory (glutamate) Laterally extending interneurons results in surround inhibition Ganglion cells have excitatory centre and inhibitory surround RFs

Question 45

what is the visual pathway like

Answer 45

Sensations from the left visual field of both eyes are transmitted to the right side of the brain Sensations from the right visual field of both eyes are transmitted to the left side of the brain Most ganglion cell axons lead to lateral geniculate nuclei The lateral geniculate nuclei relay information to the primary visual cortex in the cerebrum

Question 46

how do animals see colour

Answer 46

In humans perception of colour is based on three types of cones: red green or blue Three distinct opsin proteins Among vertebrates, mot fish, amphibians, and reptiles have very good colour vision Humans and old world monkeys are among the few mammals with the ability to see colour well Nocturnal mammals usually have a higher proportion of rods to cones in the retina to see in the dark