psyc 211 - Brain anatomy

What are the two parts of the nervous system

• The central nervous system ( CNS )→ every thing in the brain and spinal cord

• Peripheral nervous system ( PNS )→ any part of the nervous system outside the brain and spinal

• Sensory neurons and motor neurons typically span in both regions

How is myelin created in the CNS and in the PNS

• In the CNS, myelin is created by oligodendrocytes

• In the PNS myelin is created by Schwann cells

• Each Schwann cell provides one myelin

What is the blood brain barrier

• This barrier is formed by the tight arrangement of the cells that form the walls of the capillaries in the brain, which don’t let blood pass through

• Everywhere else on the body, blood is constantly flowing out of capillaries

What is extracellular fluid

• it is the liquid that leaks out of vessels (ex: blood vessels and blood plasma)

• It flows around cells providing nutrients and collecting waste

• Extracellular liquid in the body get collected into lymph vessels, which carry it to lymph nodes and lymph organs

Why does the lymphatic system does not reach the CNS and what is the cerebrospinal fluid

• that is because there are no holes in the blood vessels that pass though the brain and spinal cord.

• Rather than letting plasma directly leak out of the circulatory system, the brain makes its own extracellular solution by actively licking out what it needs from the blood

• This liquid is called cerebrospinal fluid (CSF)

What are the two types of neurons in the CNS

• projection neurons send an axon to a distal area of the brain (they synapse on neurons far away from where the axon started

• Inter neurons (only synapses on local, nearby neurons. TheIr axons don’t go far

• In the brain, projection neurons typically release glutamate and interneurons typically release GABA

What are the two types of neurons found in the PNS

• sensory neurons detect stimuli in the external and internal environment . Their cells are found throughout the body and their axons enter the CNS. These axons are afférent fibres (inputs); they carry info towards the CNS

• Motor neurons control muscle contraction and gland secretion. Their cells bodies are usually in the spinal cord, and their axons leave the CNS. These axons are efferent fivers (outputs); they carry information away from the CNS

What are nerves

• they are enclosed, cable-like bundles of axons in the peripheral nervous system

• The brain an spinal cord communicate with the rest of the body via nerves

• Most nerves are a combination of sensory axons and motor neurons

What are the two types of nerves

• Spinal nerves: we have 31 pairs of spinal nerves, nearly one pair for each vertebrae in our spine. Spinal nerves connect to the spinal cord

• We have 12 pairs of cranial nerves, which connect to the brain directly

• All cranial nerves, epxcept for #10, process movements and sensory information

• The 10th cranial nerve, the vagus, branches extensively in the upper half of the body. The vagus nerve regulates the function of multiple organs, including the heart lungs and digestive track

What is the spinal cord

• It is a long, conical structure that is approximately as thick as an adult's little finger

• The principal function of the spinal cord is to bring sensory info to the brain and to bring motor fibers to effector organs throughout the body (glands and muscles)

• The spinal cord has a certain degree of autonomy from the brain, as various reflexive control circuits are located there

Name all anatomical directions

• Neuraxis: imaginary line that runs along the length of the CNS

• Anterior: in front of

• Posterior:behind

• Superior: above

• Inferior: below

• Rosral: towards the beak

• Caudal: towards the tail

• Dorsal: towards the back

• Ventral: towards the belly

• Lateral: away from the midline

• Medial: toward the midline

What is the somatic nervous system

• it is all about the external environment

• Its afferent fibers collect sensory information from outside the body

• Its efferent filers control skeletal muscles (body movements)

What is the autonomic nervous system

• It is all about the body's internal environment

• Its afferent fibers collect sensory information from outside the body

• Its efferent fibers regulate internal bodily functions by controlling smooth muscle, cardiac muscle and glands

• The efferent branch of the ANS has two distinct parts: the sympathetic and parasympathetic divisions.

What is the sympathetic division

• It prepares the body for action, especially in life threatening situations

• It is always active to some extent, as it regulates heart rate, blood flow, and the activity of nearly every organ in the body

• When strongly stimulated, the sympathetic system increases blood flow to organs that are involved in intense physical activity, and it shunts blood away from organs that are not necessary for immdediate survival

what is the parasympathetic division

• it supports functions that occur when th wordy is in a relaxed state, when all is well

• It is always active to some extent, as it regulates urination, defacation, salvation, and sexual arousal. It is responsible for the body’s energy stores

• It is involved in “feed and breed” and “rest and digest” activities

What are the three major divisions of the brain

• forebrain

• midbrain

• Hindbrain

What is the brainstem composed of

• It refers to the stem of the brain

• It includes the medial, pons, and midbrain

What is the cerebrum composed of

• it is composed of the cerebral cortex, basal ganglia, and lambic system

Which parts of the brain are the oldest

• the medulla and pons

• These areas contain several cranial nerve nuclei, which process sensations and movements around the mouth and face

• Some brain nuclei in these areas process automatic sensations, such as a full bladder, or autonomic muscles that control heart rate or breathing

what brain nuclei are in the medulla oblongata

• It connect to the spinal cord and contains several brain nuclei:

• Cranial nerves nuclei (mouth, face, heart, stomach)

• Autonomic nuclei (breathing, heart rate, blood pressure)

• Sensorimotor relay nuclei (controlling information flow)

• The blood-brain barrier is noticeably weak in area posteema, where poisons are detected to initiate vomiting

• The medulla also contains part of the reticular formations, which regulates sleep and arousal

What are the parts of the pons

• it is a bulge in the brainstem that interconnect the cerebellum

• It contains sensorimotor relays nuclei that pass information in and out of the cerebellum as well as up and down

• It contains several cranial nerve nuclei that process information related to the face and hearing

• It contains part if the reticular information

What is the role of the cerebellum

• It does not initiate movement, but it contributes to the coordination, precision and accurate timing of movements

• Intergrafing sensory and motor information from throughout the brain and spinal cord, the cerebellum does some kind of sensimotor integration on the timescale of milliseconds/ seconds, which exerts a smoothing effect on movement and cognition

• Cerebellum function is critical for picking up a cup and drinking without spilling, particularly if you are also walking and ensuring your backpack isn’t sliding off and you are sore from a workout

• It it also plays an important role in motor learning, particularly as the body grows and changes over time (which necessitates adjustments in sensimotor intergration

• Damage to this part of tern results in jerky, exaggerated, poorly coordinated movements.

What are inputs to the cerebellum synapse in the superficial cerebrellae cortex

• It is a thin continuous layer of cells that is thickly folded in the style of an accordion

Where do neurons in the cerebellar cortex send axons

• they send them to the deep cerebellar nuclei

• in turn, those neurons project out of the cerebellum to the brain or spinal cord

Proximal

Nearby

Distal

Far away

Superficial

Located close to the surface/ exterior of animal

Deep

Located deep in the interior of the animal, far from the surface

Contralateral

Structures on the opposite side of the body

Ipsilateral

• Structure on that same side of body

• taste and smell are the only sensory systems that do not have contralateral organization

What are the parts of the midbrain

• the tectum

• The tegmentum

What is the tectum

• the tectum appears as two oaks of bumps on the dorsal , surface of the midbrain

• The two bumps are the superior colliculi, and they are involved in orienting the animal to things in peripheral visions

• The bottom two bumps are the inferior colliculli and are involved in orienting the animal to unexpected sounds

What is the tegmentum

• it includes several structures that coordinate complex species- typical movements. Some areas process pain pain and orchestrate behavioural responses to threats

What is the hypothalamus

• it is a bilateral structure made up of several brain nuclei, which generally regulate autonomic nervous system activity

• It is involved in behaviours that directly relate to survival (i.e. the four F’s: feeding, fighting, fleeing, and mating)

• Different hypothalamic nuclei control body temperature, sleep-wake cycles, hunger

• One of its most important structures is to control the endocrine system by releasing hormones into the blood via the pituitary gland

What is an hormone

• it is a chemical substance that is released into the blood by an endocrine gland. It has effects on cells in other organs

What is an endocrine gland

• it is a gland that secretes hormones into the blood.

• the master regulator of the endocrine system is the hypothalamus, as it releases hormones that regulate the function of other endocrine glands

What is the thalamus

• it is another bilateral structure that contains several brain nuclei many of which relay ascending sensory information to different regions of the cerebral cortex

• Ex: visual information from the eye passes through the lateral geniculate nuclei of the thalamus

• Many nuclei of the thalamus have widespread cortical projections

What is the cerebral cortex

• it is where sensory information enters conscious awareness

• It is where our understanding of the world is formed and where we decide how to purposefully move in the world

• It is not made up of distinct nuclei (except in birds)

• It is a multilayered structure (6 layers in mammals, 3 in reptiles)

• Neurons are interconnected between layers in a way that gives rise to cortical columns, which are thought to be partially distcint functional units

What parts are contained on the top surface of the cerebral cortex

• sulci → small grooves

• Fissures → large grooves

• Gyri → ridges between the sucking and fissures

• These convolutions increasae the surface area of the cerebral cortex

• The outermost portion of the cerebral cortex is gray matter where there is a high concentration of cell bodies

• Beneath the gray matter is white matter, which is primarily just myelinated axons

What are the different ways of cutting the brain

• coronal cut → frontal cut

• medial → toward midline

• Lateral → away from midline

• Sagittal cut → exactly in the middle (between the eyes)

• Horizontal cut

What are the four lobes of the cerebral cortex

• the frontal lobe which controls movement

• the parietal lobe which processes touch information

• The occipital lobe which processes visual information

• The temporal lobe which processes auditory information

What separates different parts of the brain

• the longitudinal fissure spearages the two hemispheres

• The lateral fissure separates the frontal lobe and the temporal lobe

• The central sulcus separates the frontal lobs and the parietal lobe

What are the primary cortical areas

• primary motor cortex (frontal lobe) contains motor neurons that synapse in the spinal cord. Different regions of primary motor cortex control different parts of the body

• Somatosensory cortex (paretial lobe) is where touch information enters the cerebral cortex. Different regions of somatosensory cortex receive information from all different parts of the body

• Primary auditory cortex (temporal lobe) is where auditory enters the cerebral cortex

• Primary visual cortex (occipital lobe) is where visual information enters the cerebral cortex

• Insular cortex when gustatory information enters the cerebral cortex

What is the sensory association cortex

• it is where perception takes place and memories are stored

• Areas of sensory association cortex nearest to the primary sensory areas receive information from only one sensory system

What is the basal ganglia

• it is referred to as subcortical structures, since it sit beneath the cerebral cortex (along with the limbic system)

• It used to be called the primitive “reptilian” brain, but it is now clear that reptiles have other forebrain areas as well

• They are a collection of subcortical nuclei. A a circuit, they regulate motivation, reinforcement learning, and habits

• Inputs to the basal ganglia come from all over the forebrain, especially the frontal lobe

• Outputs of the basal ganglia descent to midbrain and hindbrain to regulate movement. Other outputs descend the cerebral cortex to regulate sensory processing and decision making

• Many neurological disorders are associated with basal ganglia dysfunction

What is the limbic system

• it is a collection of subcortical areas that regulate emotions and the formation of episodic memories

• Its principle areas include the hippocampus, amygdala, and cingulate cortex

What is the cingulate cortex

• it is a large cortical area that overlies the corpus callosum. This region interconnects many limbic areas of the brain

What are the hippocampus and amygdala

• they are both hidden in the temporal lobe

• the hippocampus is critical for explicit memory formation

• The amygdala is critical for process in emotion, especially fear