Review final exam

The Motor Cortex• Three main areas:

– Primary motor cortex (M1) - on the precentral gyrus. The main source of voluntary motor control.

– Premotor area (PMA)– Supplementary motor area (SMA)

Central sulcusPrimary motor cortex

Supplementary motor area

Premotor area

Initiation of voluntary movements

18

• Decision to move is made by prefrontal and parietal cortex.• SMA and PMA plan movement, with input from thalamus and basal

ganglia.• Primary motor cortex receives information from SMA and PMA, and

from the primary somatosensory cortex. • Primary motor cortex sends signals via lateral pathways (direct /

indirect).

• Lateral pathways activate spinal motor neurons.

• Alpha motor neurons tell muscles to contract.

Brain motor control of movement - descending motor pathways

to the spinal cord

Lateral pathway • Connects the primary

motor cortex with the spinal motor neurons

• Responsible primarily for fine voluntary movements (e.g. tool using).

Ventromedial pathway

• Originates in the brainstem • Responsible for

subconscious, automatic movements of the torso and head (e.g. posture).

Coding of movement

19

• What is coded in the primary motor cortex? And how?

• While our movements are generally very precise, each neuron in M1 is active in a wide range of movements.

• This led Georgopoulos and his colleagues to propose the idea that movement is encoded by populations of neurons rather than individual cells.

Coding of movement

20

• Single cells in the monkey’s M1 were active during a wide range of movements. Yet each cell fired strongest during one specific direction, the preferred direction for that cell.

• The combination of direction and strength can be described as a vector – the direction of the vector is the direction of movement, and the length of the vector is the activity strength.

• Primary motor neurons control movement as a function of cell population activity, rather than as a function of single cell activity.

• Thus the actual movement is in the direction of the sum of the activity of population of all cells in M1.

Angiotensin II is produced in a reaction involving an enzyme secreted by the

a. adrenal glands.b. kidneys.c. pituitary gland.d. subfornical organs.

Copyright © Houghton Mifflin Company. All rights reserved.

Hormones Help Conserve Fluids• When either osmotic or

hypovolemic thirst is sensed, • Osmoreceptors and

barorecpetors stimulate the posterior pituitary gland to release Antidiuretic Hormone (ADH) = vasopressin.

• ADH causes the kidneys to: 1. reduce urine, 2. release the hormone renin into the blood.

• Renin triggers the conversion of angiotensin II.

• Angiotensin II causes: 1. blood vessels constrict, 2. the release of aldosterone hormone from the adrenal glands.

• Aldosterone signals the kidneys to retain sodium.

Name two proteins found in muscle fibers: ____________ ______________. myosin; actin

In the resting muscle, the interactions between actin and myosin are prevented by

a. Troponin b. Caspase c. AChd. Golgi tendons

Muscle Fibers and the Structure of Myofibrils

Muscle Fiber Contraction

Which part of the nervous system shows regeneration following axonal injury? ________________PNS

Melatonin is secreted from the ___________________. pineal gland

Sleep Spindles are mostly prevalent in:• a. REM• b. Stage 1 SWS• c. Stage 2 SWS• d. Stage 3-4 SWS

Electrophysiological (EEG) Correlates of Sleep and Waking

Thalamo-cortical interactionsof monitoring vs. sleep

Brain structures associated with sleep:• a. Dorsal raphe nuclei• b. Thalamus• c. Reticular formation• d. Locus coeruleus

Falling asleep

Sleep debt – accumulation of serotonin in ventrolateral preoptic nucleus of the hypothalamus, eventually deactivating the wakefulness circuits.

Adenosine – throughout the brain – is also related to sleep debt. Reminder: caffeine is an adenosine antagonist!

Regarding osmotic pressure, the intracellular fluid is hypertonic / isotonic / hypotonic to the extracellular fluid (circle the correct answer).

Progressive degeneration motor neurons throughout the body characterize the neurodegenerative disease _______ _______ _______. ALS = Amyotrophic Lateral Sclerosis

Masculinization of the human brain depend on:

• a. Aromatization• b. Androgens• c. Estradiol• d. Placenta

Which of the following is correct about external genitalia?

a. Ovarian hormones are responsible for development of the labial folds, clitoris, and outer part of the vagina.

b. The external genitalia are female-like in people with androgen insensitivity syndrome (AIS).

c. The external genitals develop in males and females from separate precursors.

d. AMH masculinizes the male external genitalia.

Testes produce small amounts of estrogens including estradiol

• a. True• b. False

Differentiation of external genitalia occur at:

• a. 6 weeks• b. 6-9 weeks• c. 6-12 weeks• d. None of the above

3 Stages of Sexual Prenatal Development

1 .Development of gonads (~6 weeks) Until 6 weeks – identical primordial

gonads

Genetic sex XY Chromosomes

XX Chromosomes

Gene expressio

n

Sex-determining region of Y (SRY) gene

Testis-determining factor protein encoded

Testes development

No gene expressio

n

Ovaries development

No SRY expression

2 .Differentiation of internal organs (9-12 weeks) Until ~3 month both possess a male Wolffian system and a female Mullerian

systemTestes secrete 2 hormones:

Testosterone (T; type of male androgen) Anti-Mullerian hormone

(AMH)Promote development of Wolffian

system –> seminal vesicles, vas deferens, prostate

Absence of T -> regression of Wolffian system

Degeneration of Mullerian system

Ovaries are not active in producing female fetus hormones.

T and AMH are also not produced .

Absence of AMH -> Mullerian system develops -> uterus, vagina upper portion,

fallopian tubes

3 .Differentiation of external genitalia (6-12 weeks) 5-alpha-dihydrotestosterone (DHT)

hormone created from T

Development of male external genitalia: penis, scrotum

Development of female external genitalia: labia, clitoris,

outer vagina

Chemicals that activate nociceptors:a. Lactic acidb. Vanilloidsc. Dopamined. a+b

A variety of chemicals can also activate nociceptors

Lactic acid increase in hydrogen ions in the extra cellular fluid activate nociceptors send unpleasant messages of soreness to the brain.

Vanilloids, specifically Capsaicin (found in hot peppers).

Chemicals released when a cell is damaged (potassium ions, enzymes, histamine, and ATP).

A tactile receptor, not encapsolated, provide information about touch?

• a. Merkel’s discs• b. Ruffini’s endings• c. Meissner’s corpuscles• d. None of the above

Four tactile receptors perceive touch

Type Encapsul-ated?

Size of receptive field

Quality of stimulus

Adaptation

Level of skin

Meissner’s corpuscles

Yes Small touch fast-adapting

Upper levels

Pacinian corpuscles

Yes Large vibration fast-adapting

Lower levels

Merkel’s discs

No Small touch slow-adapting

Upper levels

Ruffini’s endings

No Large stretch slow-adapting

Lower levels

+free nerve endings and endings wrapped around hair follicles

Thank you all for a great year, I wish you all good luck!

Limor