Chapter 15: Chemical Control of the Brain and Behavior Flashcards
What does proper function require?
Restricted synaptic
communication
- Sits along wall of 3rd ventricle
- Connected by a stalk to the
pituitary - Two lobes: anterior and
posterior - Integrates somatic and visceral responses in accordance with the needs of the brain
- 3 F’s
Hypothalamus
- Regulates body temperature and blood composition within a narrow physiological range in response to external environment
- responds to a sensory stimulus with humoral,
visceromotor, and somatic motor responses
Homeostasis
In cold weather, how does homeostasis work?
- Adjusts balance of sympathetic and
parasympathetic outputs of the ANS - Ex: Constrict blood vessels to minimize peripheral blood flow
- Incites appropriate somatic motor
behavioral response - Ex: Shivering
- Stimulates or inhibits release of pituitary
hormones (humoral) - Conserve water within the body – release vasopressin
3 zones of the hpothalamus
lateral, medial, periventricular
____________ zone lies next to 3rd ventricle
Periventricular
Lateral and medial zones have connections with what?
brain stem and cortex
What contains the suprachiasmatic nucleus (SCN)?
Periventricular zone
Regulates circadian rhythms (biological clock)
Suprachiasmatic nucleus
Send axons to the stalk of the pituitary
Neurosecretory cells
Posterior pituitary is _______ ________.
brain tissue
- Largest secretory cells
- Extend axons down the stalk into posterior
pituitary - release two neurohormones into bloodstream.
Magnocellular neurosecretory cells
What two neurohormones that are released into bloodstream by Magnocellular neurosecretory cells?
- Oxytocin
- Vasopressin (ADH)
- “love hormone”
- Promotes social bonding, Lactation
Oxytocin
- Regulates blood volume and salt concentration
- ADH-containing neurons receive info about
these changes and release vasopressin - Acts directly on the kidney
- leads to water retention and reduced urine production
Vasopressin (ADH)
“Master gland” of the endocrine system
Anterior lobe
What controls the anterior pituitary gland?
parvocellular neurosecretory cells
- Do not extend axons all the way into the
anterior lobe—project to the median
eminence - Communicate via bloodstream
- Secrete hypophysiotropic hormones
- via a network of blood vessels: hypothalamo-pituitary portal
circulation - hypophysiotropic hormones bind to receptors on the surface of pituitary cells
-> Activation causes pituitary cells to secrete or stop secreting hormones
parvocellular neurosecretory cells
What do parvocellular neurosecretory cells do in response to stress? (first step)
secrete corticotropin-releasing hormone (CRH—aka: CRF) into portal circulation
second step in stress response
CRH travels to anterior pituitary and
stimulates the release of
adrenocorticotropic hormone (ACTH)
third step in stress response
ACTH enters general circulation»> travels to the adrenal cortex (in kidney)
* stimulates glucocorticoid (cortisol in primates: aka “stress hormone”)
release from adrenal cortex
* Cortisol inhibits CRH release (negative feedback via hippocampus)
- Part of the PNS
- Carried out without conscious control
- commands every other innervated tissue and organ in the body
-> Widespread actions instead of pinpoint accuracy - Sympathetic division: “fight or flight”
- Parasympathetic division: “rest and digest”
Autonomic Nervous System
Mobilizes the body for a short term emergency at the expense of processes that keep it healthy long-term
Sympathetic Division
Works calmly for long-term good
Parasympathetic Division
What type of neurons does the sympathetic and parasympathetic division have?
Preganglionic neurons
- Cells bodies in thoracic and lumbar cord
- Send axons through ventral roots to synapse on sympathetic chain ganglia or within collateral ganglia in abdominal cavity
Preganglionic neurons in SYMPATHETIC division
- Cells bodies sit within brain stem and sacral spinal cord
- Axons travel within several cranial nerves and sacral nerves
- Axons travel much farther than sympathetic axons b/c
parasympathetic ganglia are
located next to or on target organs
Preganglionic neurons in PARASYMPATHETIC division
- Driven by preganglionic neurons (UMNs): cell bodies are in the CNS
- Di-synaptic control of targets
Autonomic ganglia
What neurotransmitter is at the autonomic ganglia?
ACh (acetylcholine)
Postganglionic synapse for sympathetic
- Far-reaching effects—even into
blood
norepinephrine
Postganglionic synapse for parasympathetic
- Local effect—near target
organs
- Acts entirely through mAChRs
ACh (acetylcholine)
mimic or promote muscarinic actions of ACh or
inhibit actions of NE
Parasympathomimetic
mimic or promote NE actions or inhibit muscarinic actions of ACh
Sympathomimetic
- main regulator of autonomic preganglionic neurons
- Integrates the info it receives about the body’s status, anticipates its needs, and provides neural and hormonal output
- Periventricular zone connections to brain stem and spinal cord nuclei that contain preganglionic neurons
Hypothalamus
Integrates sensory information from internal organs and coordinates output to autonomic brain stem nuclei
Nucleus of solitary tract (medulla)
solely functions to innervate and
control skeletal muscles
Somatic Motor System
Cell bodies of all somatic LMNs are in CNS
* Monosynaptic control of targets
Somatic Motor System
ACh at NMJ
Somatic Motor System
is a synaptic connection between the terminal end of a motor nerve and a muscle
neuromuscular junction (NMJ)
Locus of central control: motor cortex and brainstem
Somatic Motor System
commands every other innervated tissue
and organ in the body
* Widespread actions
* Cell bodies of LMNs in ANS are outside
CNS»> autonomic ganglia
* Disynaptic control of targets
ANS
ACh is NT in preganglionic neurons in ANS
*NE: postganglionic fibers in sympathetic
*ACh: postganglionic fibers in parasympathetic
ANS
Major locus of central control: hypothalamus
ANS
- “Brain in the gut”
- lining of esophagus, stomach, intestines,
pancreas, and gallbladder - control physiological processes involved
in transport and digestion of food - sympathetic and parasympathetic
innervation
Enteric Division of ANS
What are the 2 networks of the Enteric Division of ANS?
- myenteric (Auerbach’s) plexus
- submucous (Meissner’s) plexus
concerned with the motor aspects of gut function (e.g., peristalsis).
myenteric (Auerbach’s) plexus
concerned with the secretory aspects of gut function
submucous (Meissner’s) plexus
Axons innervate cerebral cortex, thalamus, hypothalamus, olfactory bulb, cerebellum, midbrain, and spinal cord.
Norepinephrine system in locus coeruleus
regulation of attention, arousal, sleep–wake cycles, learning and memory, anxiety and pain, mood, brain metabolism
Norepinephrine system in locus coeruleus
Activation: new, unexpected, nonpainful sensory stimuli
* Least active during rest
Norepinephrine system in locus coeruleus
innervate many of the same areas as noradrenergic (norepinephrine) system
Serotonin (5HT) system in the Raphe Nuclei
together with noradrenergic system, comprise the ascending reticular activating system
* Particularly involved in sleep–wake cycles, mood
Serotonin (5HT) system in the Raphe Nuclei
Activation: Most active during wakefulness, when aroused and active
Serotonin (5HT) system in the Raphe Nuclei
- Axons project to the striatum
- Facilitates the initiation of
voluntary movements - degeneration»_space; PD
Substantia nigra
Gives rise to two major pathways:
* Mesolimbic dopamine system: to nucleus accumbens (NAcc)
* Mesocortical dopamine system: to prefrontal cortex
Ventral tegmental area (VTA)
DA projection from midbrain to nucleus accumbens (NAcc)
* Involved in the reinforcing and rewarding aspects of drugs
* Humans and animals will self-stimulate
* Heavily investigated in many drugs of abuse
Mesolimbic Dopamine System
- Neurons lie scattered at the core
of telencephalon: medial and
ventral to basal ganglia - Function: mostly unknown,
participates in learning and
memory - First cells to die during
Alzheimer’s Disease
Basal forebrain complex
- Located in pons and midbrain tegmentum
- Provides a link between the brain stem and basal forebrain complex
Pontomesencephalotegmental complex
Damage to cholinergic system contributes to cognitive factors in ________________ disease.
Alzheimer’s
Psychoactive drugs act on the ___________.
CNS
Interfere with chemical synaptic transmission
Psychoactive drugs
LSD, Psilocybin, mescaline»>5HT2A agonists
Hallucinogens
- Cocaine and amphetamine affect dopaminergic and noradrenergic systems
- These drugs produce very high levels of DA and NE in the synaptic cleft
- Sympathomimetic
Psychomotor stimulants
