The brain and sensory perception Flashcards
what does the forebrain become
The Forebrain leads to the Telencephalon and Diencephalon
what does the telencephalon become
The Telencephalon leads to the Cerebrum (including the cerebral cortex, white matter basal nuclei)
what is the structure of the telencephalon
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
what is the cerebral cortex used for
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
what does the CNS develop from
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
what fills the canal of the spinal cord and 4 ventricles of the brain
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
what are the two types of neuronal matter
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
What are the four regions of the cortex
Frontal lobe, temporal lobe, occipital love, parietal lobe
what does the frontal lobe do
Frontal lobe: Motor cortex (Controls skeletal muscles), Prefrontal cortex (decision making, planning), Broca’s area (forming speech)
what does the temporal lobe do
Temporal lobe: Auditory cortex (hearing), Wernicke’s area (comprehending language)
what does the occipital lobe do
Occipital lobe: Visual cortex (processing visual stimuli and pattern recognition) and Visual association cortex (combining images and object recognition)
what does the parietal lobe do
Parietal Lobe: Sensory association cortex (integration of sensory information) and Somatosensory cortex (sense of touch)
what can happen when the frontal lobe is damaged
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
what is Broca’s area
Broca’s area in frontal lobe is active when speech is generated– Patients with damage in this are can understand language, but cannot speak*
what is Wernicke’s area
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
how is the cerebral cortex lateralized
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
what does the Diencephalon become
The Diencephalon contains the Thalamus, Hypothalamus, Pineal gland, and Pituitary gland.
what does the Thalamus do
The Thalamus acts as the relay centre for most sensory information
What are the four functions of the hypothalamus
The Hypothalamus acts on Homeostasis and hormones with 4 main functions:
- Tt controls Thermoreceptive neurons in heat loss centre (controlling vasodilation and sweating) and heat gain centre (controlling shivering) to maintain body temperature at 37ºC
- 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)
- It regulates appetite (hunger and satiety centres)
- 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
what does the Pineal gland do
The Pineal gland releases melatonin, which plays an important function in maintaining diurnal rhythms; capillaries form CSF
what does the midbrain become, and what are the two parts of this structure
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)
what does the tectum do
Superior and Inferior colliculi control sensory motor integration
What does the Tegmentum do (5 things)
- 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
what does the hindbrain become
The Hindbrain slits into two parts
The Metencephalon which has the pons and cerebellum
And the Myelencephalon which becomes the Medulla oblongata
what does the metencephalon contain
The Metencephalon contains the Pons and the Cerebellum
what do the pons do
- 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
what does the cerebellum do
The Cerebellum controls motor coordination and learned motor tasks
what does the myencephalon contain
The Myencephalon is at the bottom of the brain stem and contains the Medulla Oblongata
what does the medulla oblongata do
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.
what are the four types of receptor
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
what do mechanoreceptors do
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.
How are touch receptors distributed
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
what do primary sensory neurons do
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)
what do secondary and third-order neurons
Second-order neurons relay responses from the SC to the thalamus
Third-order neurons relay information from the thalamus to the somatosensory cortex
what does the Somatosensory cortex have
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.
what are pain receptors like
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
how do animals see light
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
what are ocelli
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
what are compound eyes
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
what are single lens eyes
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
how do animals convert light into graded electrical signals
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
how do octipi and human eyes differ
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.
how is the distribution of photoreceptors in the human body
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)
what is retinal circuitry like
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
what is the visual pathway like
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
how do animals see colour
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
