Functional Neuroanatomy

Fill in the blanks

Frontal Lobe function

Sense of self, associated with reasoning and higher cognition

Temporal Lobe Function

auditory system and limbic system

Parietal lobe function

processing of sensory information and spatial navigation, language processing

occipital lobe

interpreting visual stimuli (primary visual cortex)

efferent sensory axons

from brain to body

afferent motor axons

neurons from body to brain

Fill in blanks + fissures/sulcus

Forebrain parts

telencephalon + diencephalon

Midbrain parts

mesencephalon

Hindbrain parts

metencephalon + myelencephalon

telencephalon parts

cerebral cortex, olfactory system, lateral ventricle

diencephalon parts

hypothalamus, thalamus, third ventricle

mesencephalon parts

tectum, tegmentum, cerebral aquiduct

metencephalon parts

cerebellum and pons

myelencephalon

medulla oblongata

embryo development of brain

Steps of development of nervous system 1 formation of the neural groove (dent in the system)
2 walls of the groove (neural folds) come together and fuse -> neural tube formed [ENTIRE CNS DEVELOPS FROM THE NEURAL TUBE]
3 bits of neural ectoderm that are pinched off – neural crest [FROM WHICH PNS WILL DEVELOP]

Anterior/rostral

Toward the nose

Posterior

Toward the tail

Dorsal

upper surface area

Ventral

Lower surface area

Medial

Toward the midline

Lateral

Away from the midline

Ipsilateral

2 structures on the same side of the body

Contralateral

2 structures on opposite side of the body

saggital plane

midline of the braind

Coronal plane

Plan that runs ear to ear

Ventricular system function and anatomy

Creates CSF

Meninges Anatomy

Ventral Ramus

Nerves of spinal cord, collects information for the brain

Dorsal Ramus

Nerves of spinal cord, commands muscle

1. Cingulate Gyrus 2. thalamus 3. corpus callosum 4. pineal body 5. fornix 6. hypothalamus 7. pons 8. cerebellum 9. medulla

Corpus Callosum function

Connects communication between the two hemispheres

Pineal Body Function

Neuroendocrine organ responsible for secreting melatonin

Fornix

Part of limbic system, connects the hippocampus and hypothalamus

Hypothalamus Function

Controls homeostasis

Pons Function

Connects the cerebellum and cerebral cortex

Cerebellum Function

Important movement control center, receives input from spinal cord and pons

Medulla Function

Contains sensory and motor neurons that control respiration, cardiac function, vasodilation and several reflexes (vital function control)

What is the resting potential?

The electrical potential difference across the plasma membrane when the neuron is not in a excited stage (-65mV)

Ionic concentration (high/low) inside and outside the cell during resting potential

Inside: High potassium (K+), low sodium (Na+) and chloride (Cl-), Outside: high sodium, high chloride, low potassium

Sodium-Potassium pump

Pump involved to maintain the resting potential, lets 2 K+ in, while 3 Na+ are pumped out. Uses ATP

Ion Channels vs Ion Pumps

Ion channels facilitate ion diffusion, similar to opening a gate (no energy), whereas ion pumps actively pump out/in ions (energy)

Membrane Anatomy

Phospholipid bilayer, hydrophilic heads, hydrophobic tails + channels + pumps

Action Potential Definition

An action potential is a signal that conveys informations over distance in the nervous system

Stages of Action Potential

1. Threshold reaching, 2. Rising Phase 3. Overshoot (+40mV), 4. Falling phase 5. Undershoot 6. refractory period

Threshold action potential meaning

The threshold is the membrane potential at which enough voltage-gated sodium channels open so the relative ionic permeability of the membrane favors sodium over potassium (initiation of the action potential)

Rising Phase action potential meaning

When the outside of the membrane has a negative electrical potentail, there is a large driving force on Na to enter the cell. Therefore, through rapid Na movement into the cell, the membrane depolarizes

Overshoot action potentail meaning

The relative permeability of the membrane greatly favors sodium, therefore sodium enters the cell where there is already a lot of K+ making it temporarily positive (40mv)

Falling phase action potential meaning

1. voltage gated sodium channels are inactivated 2. voltage gated potassium channels open --> potassium leaves cell, --> depolarization of cell --> negative membrane potential

Undershoot action potential meaning

The open voltage gated potassium channels stay open a little longer than needed, creating an undershoot

Absolute refractory period

Sodium channels are still inactivated from falling phase, therefore a new action potential is impossible

Relative refractory period meaning

Part where the cell is hyperpolarizing to resting potential, action potentials are possible but the threshold is higher

Action potential transfer through myelin/schwann

Myelin sheets insulate to facilitate fast transfer, action potential occurs in nodes of ranvier between myelin sheets.

Steps of chemical neurotransmission

Small neurotransmitters

Single amino acid neurotransmitters that are able to bind to ionotropic receptors to illicit APs (e.g. glutamate)

Large neurotransmitters

Neuropeptides that bind to G-coupled receptors and manipulate a cell through second messenger systems (e.g. epinephrine)

Gap junction and

Channels between adjacent cells that mediate the transfer of small neurotransmitters and electrical transmission

Hypothalamus endocrine function

Send and regulate the pituitary gland hormone release through releasing factors

How is the anterior pituitary activated by the hypothalamus?

Hypothalamic releasing factors travel to the anterior pituitary gland through a capillary system.

Hormones released by the anterior pituitary gland

thyrotropin, growth hormone, corticotropin, FSH, LH, prolactin

How is the posterior pituitary activated by the hypothalamus

Long axises from the hypothalamus extend into the posterior pituitary which activate the gland

Hormones released by the posterior pituitary gland

ADH, oxytocin

How are sex hormones regulated?

Hypothalamus --> anterior pituitary gland --> fsh+lh --> gonads --> estradiol/ testosterone --> negative feedback to hypothalamus and pituitary

How does the SRY gene affect development?

The SRY gene stimulates testes development through stimulating wolfian ducts to develop and mullarian ducts to degrade. Absence of SRY does the opposite. In reality, more genes are involved

What is a steroid hormone

Steroid hormones are derived from cholesterol and can therefore travel through the membrane. Within the cell, they bind to nuclear receptor. Together with the nuclear receptor, they bind directly to DNA to alter expression. The steroid hormone does not use second messengers as opposed to other hormones

Organisational vs activational effects of hormones

Organisational hormones organise tissue in an irreversible way (testosterone, estradiol), activational hormones activate usually temporary processes like hunger

What happens when Leptin levels rise?

A rise in leptin levels stimulates the release of MSH and CART from arcuate nucleus neurons. These peptides act on the brain, in part by activating the MC4 receptor, to inhibit feeding behavior and increase metabolism.

What happens when Leptin levels fall?

A fall in leptin levels stimulates the release of NPY and AgRP from arcuate nucleus neurons (situated in the hypothalamus), and the release of MCH and orexin from neurons in the lateral hypothalamic area. These orexigenic peptides act on the brain to stimulate feeding behavior and decrease metabolism.

Insulin

Is released into the bloodstream by the β cells of the pancreas Glucose needs insulin to be transported in the other cells of the body
Important during anabolism AND catabolism
When the levels of glucose are high in the blood: levels of insulin decrease
When levels of glucose are low in the blood: levels of insulin increase
insulin acts directly on the hypothalamus

Ghrelin

Released in the stomach and small intestines
Stimulates hunger through NPY neurons in the hypothalamus

MCH and food

Leptin sensitive cells in the arcuate nucleus release MCH when leptin levels drop
MCH system informs the cortex of leptin levels
MCH induces feeding behaviour

Orexin and food

Receive input from arcuate nucleus
Stimulates feeding behavior
Levels rise when leptin levels decline
Orexin promotes meal initiation, MCH prolongs consumption
Also a role in wakefulness

CCK and food

released with gastric distension --> satiety

Dopamine and feeding

Dopamine induces food seeking behavior, however, does not play a big role in enjoyment of food

Serotonin and feeding

Serotonin is low in postabsorptive period, rise in anticipation of food and spike during a meal especially to carbohydrates

High level motor control

Associated with strategy, involves the basal ganglia and neocortex

Mid level motor control

represented by the motor cortex and cerebellum, is concerned with tactics: the sequences of muscle contractions, arranged in space and time, required to smoothly and accurately achieve the strategic goal.

Low level motor control

The lowest level, represented by the brainstem and spinal cord, is concerned with execution: activation of the motor neuron and interneuron pools that generate the goal-directed movement and make any necessary adjustments of posture.

Lateral corticospinal tract

Distal muscle control
Cortex (area 4/6) --> internal capsule between telencephalon and thalamus --> cerebral peduncle --> pons --> medulla (medullary pyramid) --> runs down the ventral surface of the medulla (pyramidal tract) --> spinal cord

Ventromedial pathways (function)

voluntary movement of proximal muscles through multiple pathways, all originate in the brain stem

vastibulospinal tract (ventromedial)

originates in vastibular nuclei of the medulla and balances the body

tectospinal tract (ventromedial)

originates in the superior colliculus and receives input from auditory and visual stimuli. Helps orient head and eyes

Pontine reticulospinal tract (ventromedial)

originate from the reticular formation of the brain stem. Enhances antigravity reflexes of the spinal cord in the lower limbs

Medullary reticulospinal tract

Liberates the antigravity muscles from reflex control
Counteracts pontine tract to keep balance

Basal ganglia and movement

The basal ganglia may facilitate movement by focusing activity from widespread regions of cortex onto the SMA. Importantly, however, they also serve as a filter that keeps inappropriate movements from being expressed.

Area 4 of the cortex

Primary motor cortex (M1)

Area 6 of cortex

Higher motor control
Lateral area --> premotor area (PMA)
Medial region --> supplementary motor area (SMA)

a. eye lids
b. pupil
c. sclera
d. iris
e. retina
f. ciliary muscle
g. cornea
h. iris
i. fovea
j. optic nerve
k. lens
l. conjuctiva
m. sclera

1. optic nerve
2. optic chiasm
3. lateral geniculate nucleus (LGN)
4. optic tract
5. visual cortex

Laminar organisation of the retina

How does light get transformed into neural activity

Light enters eye --> refraction into the fovea --> passes through ganglion and horizontel cells --> hits the photoreceptors --> transformed into neural activity --> horizontal cells --> ganglion cells --> action potential

Cones

Photoreceptors responsible for more detail and help with spatial sensitivity; have different types of photo pigments that are sensitive to different wavelengths of light

Rods

contain more membranous disks; help with night vision because they are more sensitive to light; responsible for seeing contrast

LGN

Situated in the dorsal thalamus, consists of 6 layers to filter and relay visual information

non-thalamic visual targets

pineal body --> melatonin / circadian rhtyhms
superior colliculus --> eye and head movement

Light, visual hemifields and optic chiasm

Light form the right hemifields, hits the left part of the eye, light from the left hits the right part of the eye. In the optic chiasm, input from the right hemifields goes to the left brain, and input from left hemifield goes to the right brain